Polishing apparatus and polishing method

ABSTRACT

The present invention realizes a polishing apparatus capable of chamfering an end face of a large-sized substrate at a high precision for a table unit for mounting the substrate. A substrate is mounted on a table unit and is fixedly held in a predetermined reference state. A first polishing unit includes a polishing grind stone for polishing an end face of the substrate held on the table unit and substrate side edge portion supporting means for supporting the lower surface of a side edge portion of the substrate in the vicinity of the end face of the substrate to be polished by the polishing unit. The first polishing unit is moved together with the substrate side edge portion supporting means by a first polishing unit moving means along the end face of the substrate while the polishing grind stone is polishing the end face of the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is U.S. national phase filing under 35 U.S.C. §371 of PCT/JP2005/016045 filed Sep. 1, 2005 and claims priority from Japanese Application No. 2004-291950 which was filed on Sep. 3, 2004.

TECHNICAL FIELD

The present invention relates to a polishing apparatus and a polishing method for polishing an end face of an outside surface of a substrate.

BACKGROUND ART

Normally, a brittle substrate (e.g., semiconductor wafer, glass substrate, quartz substrate, ceramic substrate) is subjected to a process of chamfering of an end face of the substrate. Also in a bonded substrate for which single substrates are bonded to each other, an end face of each of the substrates is chamfered. Particularly, this bonded substrate is often used for a panel of a liquid crystal display (LCD), which is a type of flat panel display (FPD). In addition, the bonded substrate is used for a plasma display panel (PDP), which is also a type of FPD other than liquid crystal display panel (LCD), an organic EL panel or a transmissive liquid crystal projector substrate and reflective liquid crystal projector substrate, which are included in a liquid crystal projector, or the like. Further, the bonded substrate is used for a field emission display (FED). The size of the bonded substrate for such use varies, ranging from a small size for liquid crystal display panel used in a cell phone to a large size for television and display. In a boded substrate, a large-sized mother substrate is cut to a predetermined size so as to manufacture individual FPDs. In manufacturing an FPD, yields of a cutting step and a chamfering step for the bonded substrate are reflected on the cost of manufacturing an FPD.

In the present invention, a single-plate glass substrate and a bonded glass substrate will be described as an example of the variety of substrates described above. FIGS. 23 and 24 are respectively the plan view and side view of a liquid crystal display (LCD) panel D, which is cut into an individual unit from a large-sized mother liquid crystal panel. In this liquid crystal display (LCD) panel D, spacer is sprayed on either side of two glass substrates G1 or G2, and both substrates are bonded to each other to form a gap portion between the substrates. Liquid crystal L is injected into the gap portion. Thereafter, the liquid crystal L is enclosed with gap portion sealing material V. As a result, the liquid crystal display (LCD) panel D is formed. Transistors 20 for driving individual pixels are formed on the lower glass substrate G2. An electrode terminal 21, which is an input terminal of each of the transistors 20, is formed on a side edge portion Q of the lower glass substrate G2 for external connection. The side edge portion Q of the glass substrate G2 is exposed and not covered by the upper glass substrate G1. The electrode terminal 21 is connected to an external circuit as an input terminal of each of the transistors 20.

The electrode terminals 21 are short-circuited to each other with a short-circuit electrode 22, which is formed on the side edge Q, such that the transistors 20 do not have dielectric breakdown by static electricity, which occurs on a surface of a substrate during manufacturing. The glass substrate G2 provided with the short-circuit electrode 22 is broken (cut) along a scribing line (scratching line or cutting line) 23 formed between each of the electrode terminals 21 and the short-circuit electrode 22 at a final stage in the process of manufacturing of the liquid crystal display (LCD) panel D. As a result, the side edge portion Q of the glass substrate G2, having a width W, is separated. Accordingly, the short-circuit of the electrode terminals 21 to each other by the short-circuit electrode 22 is released. FIG. 25 is a perspective view schematically showing the steps of processing the side edge portion Q of the glass substrate G2. A method for this process will be described with reference to FIG. 25.

As shown in Portion (A) of FIG. 25, the short-circuit electrode 22 is formed on the side edge portion Q of the glass substrate G2, which makes up one side of the liquid crystal display (LCD) panel D, wherein the short-circuit electrode 22 short-circuits the plurality of electrode terminals 21 to each other. At the final stage in the process of manufacturing the liquid crystal display (LCD) panel D, a scribing line 23 is formed between each of the electrode terminals 21 and the short-circuit electrode 22 along the short-circuit electrode 22 as shown in Portion (B) of FIG. 25. The short-circuit electrode 22 on the side edge portion Q of the glass substrate G2 is broken along the scribing line 23 and separated as shown in Portion (C) of FIG. 25. Next, as shown in Portion (D) of FIG. 25, an end face 24 of the glass substrate G2 is polished, and an edge 25 where the surface of the glass substrate G2 having the electrode terminals 21 formed thereon and the end face 24 contact each other is chamfered (light-chamfered) while the end face 24 of the glass substrate G2 having the electrode terminals 21 formed thereon is polished.

In addition, edges 26 along the vertical direction of both sides of the end face 24 of the glass substrate G2 are also chamfered by polishing. As shown in Portion (D) of FIG. 25, each edge of the end face 24 of the glass substrate G2 is polished for the following reason.

When an FPD such as a liquid crystal display panel is manufactured, a mother bonded substrate for which substrates are bonded to each other is scribed and broken, so that display panel substrates are cut therefrom. In each of the cut display panel substrates, stress remains on both sides (edge portions of end faces of the cut substrate) of a scribing line formed at the time of scribing using a scribing cutter. There is a concern that this remaining stress may cause chipping and the like at steps subsequent to scribing and breaking steps, which results in a defective product when a display panel substrate is produced. Therefore, in a cut substrate, an end face of the substrate on which scribing and breaking are performed is chamfered by polishing and the like. As a result, the portion with remaining stress is removed. A wet polishing apparatus is normally used in the process of manufacturing a liquid crystal display (LCD) panel, thereby preventing adverse effect of heat due to a large amount of polishing.

The polishing process described above shows an example of polishing only one end face of a liquid crystal display (LCD) panel. However, in an actual process of manufacturing a liquid crystal display (LCD) panel, it is necessary to polish two end faces or three end faces. Further, depending on the use, there may be a case of polishing all four end faces.

Reference 1 discloses a polishing apparatus for polishing end faces of an LCD panel. In this polishing apparatus, four polishing machines are provided in order to polish each of the end faces of a glass substrate which is set at a predetermined position on a suction table unit. The polishing machines are positioned to contact edges of the end faces to be polished, and the polishing machines are simultaneously moved along the edges, so that the edges are simultaneously polished and chamfered.

The polishing apparatus further includes: a suction table unit for suctioning and fixing the set LCD panel (work); a table unit moving mechanism for moving the suction table unit in the X and Y directions along a horizontal plane and rotating the suction table unit by angle θ along the X-Y plane (horizontal direction) in the X-Y plane; and a CCD camera for capturing an alignment mark provided on the work set on the suction table unit. Furthermore, the polishing apparatus includes an alignment mechanism for moving the suction table unit by the table unit moving mechanism such that the polishing apparatus recognizes the displacement of the work based on the image data on the CCD camera and corrects the amount of the displacement. Furthermore, the polishing apparatus includes: a polishing machine transfer mechanism for moving the four polishing machines in the X, Y and Z directions; a polishing moving mechanism for simultaneously moving the polishing machines corresponding to the edges targeted for processing along the respective edges and polishing the edges; and a control section for controlling the polishing machine moving mechanism.

In the polishing apparatus, when four edges of a work are polished, the work is fixed and the edges are polished while the four polishing machines are simultaneously moved along the respective edges. As a result, time required for polishing is significantly shortened. Also, since it is not necessary to move or rotate the work for each polishing, the displacement resulting from the movement of the work and the like does not occur. Thus, polishing can be performed at a high precision. Further, since it is possible to polish all the end faces on one table unit, it is not necessary to provide an apparatus for rotating the table unit. Thus, a large space is not required, thereby realizing miniaturization of the polishing apparatus.

The following description refers to all the chamfering, including C-face chamfering and round chamfering between the end faces and the surfaces of the substrate in the horizontal direction; C-face chamfering and round chamfering formed by the end faces of the substrate in the vertical direction; and processes of polishing parts other than the edges of the end faces of the substrate.

FIG. 26 is a side view for describing an essential structure of another conventional polishing apparatus for chamfering an end face of a substrate. This polishing apparatus 30 includes: a polishing unit 31; and a table 32 for suctioning and holding a substrate 33 targeted for chamfering. The table 32 vacuum-suctions and holds the rectangular-shaped substrate 33 and is rotatable about a vertical axis by an arbitrary angle θ by a rotating means (not shown). The bottom portion of the table 32 is fixed to a rotating base of the rotating means (not shown).

The polishing unit 31 includes: a spindle motor 34; a polishing head 36 having a rotatable polishing grind stone set 35; a pair of image capturing devices 37 (e.g., CCD camera or the like) for capturing a pair of alignment marks provided on the substrate 33; and a polishing head moving mechanism 38 for moving the polishing head 36 in the up-down direction. In this polishing apparatus 30, the vertical direction is defined as the Z-axis direction, the side direction in which the table 32 is positioned with respect to the polishing unit 31 is defined as the Y-axis direction, and the direction perpendicular to the Z-axis direction and the Y-axis direction is defined as the X-axis direction. The polishing head moving mechanism 38 moves the polishing head 36 in the Z-axis direction and positions the rotating polishing grind stone set 35 such that the rotating polishing grind stone set 35 is positioned for polishing an edge 33 a of the substrate. The polishing unit 31 having the polishing head moving mechanism 38 is moved independently in the X-axis direction and the Y-axis direction by a polishing unit moving mechanism (not shown). The polishing unit 31 is controlled by a control section (not shown) such that a rotatable predetermined polishing grind stone 35 i of the polishing grind stone set 35 contacts the substrate 33 and moves along the edge 33 a of the substrate 33 while rotating.

The polishing grind stone set 35 includes a plurality of polishing grind stones 35 i (i=1, 2, . . . ), each having the substantially disc. The polishing grind stones 35 i are concentrically stacked in multiple layers and held by a supporting shaft. Each of the polishing grind stones 35 i is a grind stone for chamfering. The reason that the polishing grind stones 35 i are stacked in the multiple layers is to shorten the time required for any change of tools for chamfering (e.g., replacement due to the wearing-out of the grind grains of a polishing surface of each of the polishing grind stones 35 i). In the polishing grind stone set 35, when a polishing surface of a polishing grind stone 35 i is worn out and no longer capable of polishing an edge of the end face 33 a of the substrate 33 into a predetermined shape, the supporting shaft of the polishing grind stones 35 i is moved in the Z-axis direction by a predetermined pitch by the polishing head moving mechanism 38, and then a new polishing surface of a polishing grind stone 35 i which is not worn out will perform chamfering. If the polishing grind stones 35 i have “n” number of layers, a polishing surface of each of the polishing grind stones 35 i of first layer, . . . i-th layer, . . . n-th layer is moved in order in the up-down direction so as to polish the end face 33 a of the substrate 33 according to the wearing-out of each of the polishing grind stones 35 i.

The pair of the image capturing devices 37 captures a pair of alignment marks, respectively, provided on the substrate. A control section (not shown) of the polishing apparatus 30 stores positional data of the pair of alignment marks in a memory provided in the control section. When coordinates of the central (reference) position S of a mounting surface of the table 32 are denoted as (X0, Y0, Z0), a plurality of suction grooves are provided on the table 32 wherein the plurality of suction grooves are point-symmetrical with respect to each other having the central position (X0, Y0) as their center. The suction grooves of the table 32 are negative-pressured by suction means (e.g., vacuum pump or suction pump), so that the substrate 33 targeted for chamfering is vacuum-suctioned and fixed.

Further, Reference 2 discloses a polishing apparatus for polishing an end face of a glass substrate, the polishing apparatus having a function of a cleaning suspension liquid including polishing powder generated at the time of polishing. In this polishing apparatus, a table unit is rotatable in a horizontal state, and two polishing machines are provided so as to face the edges on both sides of a work fixed to the table unit. The table unit is moved while grind stones of the polishing machines are in contact with the respective edges on both sides of the work. As a result, each edge of the substrate (work) is polished by the polishing grind stone. When polishing is completed, the table unit is rotated by 90 degrees, and a pair of edges of the work which is not polished yet is polished. Hence, the polishing of all the edges of the work is completed.

Reference 3 discloses a polishing apparatus for polishing edges of a unit liquid crystal display panel after cutting a large-sized mother liquid crystal panel into unit liquid crystal display panels. This polishing apparatus is characterized in that it includes polishing bases for the unit liquid crystal display panel which correspond to unit liquid crystal display panels of various sizes. The polishing apparatus includes a plurality of polishing bases which are capable of moving in any direction in accordance with the size of a unit liquid crystal display panel.

[Reference 1] Japanese Laid-Open Publication No. 08-197402

[Reference 2] Japanese Laid-Open Publication No. 10-58293

[Reference 3] Japanese Laid-Open Publication No. 2003-275955

DISCLOSURE OF THE INVENTION

In a recent FPD, panels having a large size have been required. Thus, the size of a mother substrate panel has been also increased. Mother liquid crystal panels of the sixth generation and the seventh generation have been increasingly used. A mother liquid crystal panel of the sixth generation has the size, for example, of 1500 mm×1850 mm. A mother liquid crystal panel of the seventh generation has the size, for example, of 1870 mm×2200 mm. When a substrate of a mother liquid crystal panel having such sizes is cut into a plurality of substrates of liquid crystal display panels, and edges and end faces of a substrate of a cut liquid crystal display panel are polished, larger-sized table units which are used in the polishing apparatuses, as disclosed in References 1 and 2, are required. It is not easy to secure the flatness of the upper surface of a large-sized table unit where a substrate is mounted, the precision of which is as good as that of a normal-sized table unit. When a substrate is mounted on the upper surface of a table unit incapable of securing the required flatness and the substrate is suctioned and fixed, undulations and the like occur on an end face of a substrate. As such, there is a concern that an end face of a substrate may not be polished at a high precision when undulations and the like occur on the substrate.

Also, when the table 32 is made small-sized, and the large-sized substrate 33 is suctioned and fixed to the small-sized table 32, a circumferential portion of the substrate 33 is bent downward, as shown in FIG. 27. When the substrate 33 is chamfered, it is normally preferable, as shown in FIG. 26, that the substrate 33 is fixed such that the edge 33 a of the substrate 33 is protruding outward by 5 to 15 mm from a mounting surface of the table 32. However, when the substrate 33 is large-sized and thinned, and the table 32 is small-sized as shown in FIG. 27, a protruding portion of the substrate 33 from the table 32 becomes larger. Thus, the angle of bending of that portion also becomes larger. In this case, it is difficult to position the rotating polishing grind stone 35 i with respect to the edge 33 a of the substrate 33. In particular, when undulations occur on the end face 33 a of the substrate 33, thus causing the position of the edge 33 a with respect to Z-axis direction to become unstable, it is not easy to position the polish grind stones 35 i at a high precision with respect to the edge 33 a of the substrate 33 to perform a polishing work in a continuous manner. This causes a problem that high precision chamfering cannot be performed.

It is considered that the table 32 is changed to one having a different size such that the edge 33 a of the substrate 33 is protruding outward by about 5 to 15 mm from the mounting surface of the table 32 in accordance with the change of the size of the substrate 33. However, in this case, time required for any change of tools (e.g., replacement of the table 32) becomes longer, resulting in reduced production efficiency.

A polishing apparatus disclosed in Reference 3 is structured to use a plurality of movable tables so as to correspond to substrates of various sizes. However, in the structure of supporting the substrate with a plurality of tables, each of the plurality of tables supports a portion of the substrate but cannot support the entire substrate. Therefore, a portion of the substrate between each table bends, causing a concern that all the edges of the substrate may not be supported without bending. As a result, the polishing apparatus disclosed in Reference 3 has a problem that it cannot chamfer a substrate at a high precision.

The present invention is made in view of such conventional problems. The objective of the present invention is to provide a polishing unit, a polishing apparatus and a polishing method for an end face of a substrate for corresponding to substrates of various sizes and stably supporting a circumference of a portion to be polished at an end face of a large-sized substrate so as to perform chamfering at a high precision.

A polishing apparatus according to the present invention includes: a table unit, having a substrate mounted thereon, for fixedly holding the substrate in a predetermined reference state; a first polishing unit including a polishing grind stone for polishing an end face of the substrate held on the table unit and substrate side edge portion supporting means for supporting a lower surface of a side edge portion of the substrate in a vicinity of the end face of the substrate to be polished by the polishing grind stone; and a first polishing unit moving means, together with the substrate side edge portion supporting means, for moving the first polishing unit along the end face of the substrate while the polishing grind stone is polishing the end face of the substrate.

A polishing method according to the present invention includes: a holding step of mounting the substrate on the table unit and fixedly holding the substrate in the reference state by the table unit; a supporting step of supporting a side edge portion of the substrate held on the table unit by the substrate side edge portion supporting means of the first polishing unit; and a moving step of moving, while the polishing grind stone of the first polishing unit is polishing the end face of the side edge portion supported by the substrate side edge portion supporting means, the first polishing unit along the end face being polished by the first polishing unit moving means.

According to the present invention, the substrate side edge portion supporting means of the first polishing unit supports a side edge portion of a substrate in the vicinity of an end face of the substrate to be polished. Therefore, it is possible to accurately position the polishing site of the end face of the substrate at a predetermined height. Further, since the substrate side edge portion supporting means is moved together with a polishing grind stone, it is possible to polish the end face of the substrate without sustaining any influence of undulations, bending and the like of the substrate.

Further, with the provision of means for holding the upper surface of the side edge portion of the substrate with the first polishing unit, it is possible to prevent, by the polishing grind stone, the polishing sites moving in order from rising at the time of polishing. Therefore, it is possible to position the polishing sites at a high precision, thereby stably polishing at a high precision without sustaining any influence of displacement in the thickness direction of the substrate.

The substrate side edge portion supporting means supports the lower surface of the substrate by a member having a low friction coefficient. Thus, the substrate side edge portion supporting means can move smoothly while supporting a side edge portion of the substrate.

The substrate side edge portion holding means supports the lower surface of the substrate by a member having a low friction coefficient. Thus, the substrate side edge portion holding means, together with the substrate side edge portion supporting means, moves smoothly while holding the side edge portion of the substrate from both sides thereof.

When a member having a low friction coefficient is a free bearing, a large ball included in the free bearing smoothly rotates and moves while supporting a side edge portion of the substrate in the vicinity of the polishing site of an end face of the substrate with a point contact. Thus, the friction coefficient of the free bearing with respect to the lower surface of the substrate is small, and there is no limitation imposed on the direction of contact of the lower surface of the substrate and movement of the free bearing. Therefore, it is possible to assuringly prevent the substrate from sustaining any damages.

The table unit includes a center table for suctioning and holding the central portion of the lower surface of the substrate. Thus, it is possible to prevent a rotation and a positional displacement of the substrate even if a rotating moment is generated at the time of polishing.

The table unit includes a plurality of substrate auxiliary supporting means, the plurality of substrate auxiliary supporting means being arranged around the center table to respectively support side portions of the lower surface of the substrate held on the center table. Thus, if the size of the substrate becomes larger, it is possible to prevent the occurrence of an undulation on the substrate by supporting the substrate between the center table and the polishing unit by the substrate auxiliary supporting means.

The substrate auxiliary supporting means of the table unit includes an auxiliary supporting base for supporting the lower surface of the substrate, and the auxiliary supporting base is structured to support the lower surface of the substrate by a member having a low friction coefficient. Thus, it is possible to supporting the substrate without causing any damages to the lower surface of the substrate.

The lower surface of the substrate is supported by a free-bearding of the substrate auxiliary supporting means of the table unit. Thus, when the table unit holding the substrate is rotated, the substrate is supported without causing any positional displacement and there is no concern of causing any damages to the lower surface of the substrate.

Vacuum-suction means is provided on the portion which contacts the lower surface of the substrate auxiliary supporting means, the vacuum-suction means suctioning and holding the lower surface of the substrate. Thus, it is possible to solidly support the substrate. As a result, even if the size of the substrate becomes large, there is no concern of the substrate rotating and causing a positional displacement even if a rotating moment with respect to the substrate becomes large at the time of polishing an end face.

The substrate auxiliary supporting means includes a sliding mechanism for sliding the auxiliary supporting base closer or away from the center table. Thus, it is possible to change the position of the substrate auxiliary supporting means in accordance with the size of the substrate, and it is also possible to stably support the substrate. In addition, there is no need for any change of tools (e.g., change of tables) in order to correspond to substrates of various sizes.

The table unit further includes a table rotating mechanism for rotating the center table. Thus, even if the substrate mounted and held on the table unit is rotated in a horizontal direction with respect to a reference position, it is possible correct the posture of the substrate by rotating the table unit such that the polishing line for the substrate and the moving direction of a polishing grind stone are parallel to each other.

The first polishing unit and the first polishing unit moving means are attached to a first polishing unit holding body, the first polishing unit holding body having a horizontal beam arranged along the end face of the substrate held on the table unit, and the first polishing unit holding body is movable in a vertical direction with respect to the horizontal beam. Thus, it is possible to polish three end faces of the substrate mounted on the table unit using the polishing units without rotating the table unit. In addition, it is possible to polish four end faces of the substrate by rotating the table unit at least once by 90 degrees or 180 degrees. Further, when each of the polishing units reaches an end portion of the end face being currently polished, it is possible to chamfer a corner portion of the substrate by setting the moving direction of the polishing unit appropriately. Further, it is possible to easily change the chamfering of the corner portion of the substrate to either C-face chamfering or round chamfering.

A polishing apparatus according to the present invention further includes: a second polishing unit including a polishing grind stone for polishing an end face, the end face being positioned on the opposite side of the end face to be polished by the first polishing unit for the substrate held on the table unit and substrate side edge portion supporting means for supporting a lower surface of a side edge portion of the substrate in a vicinity of the end face of the substrate to be polished by the polishing grind stone; and second polishing unit moving means, together with the substrate side edge portion supporting means, for moving the second polishing unit along the end face of the substrate while the polishing grind stone is polishing the end face of the substrate, wherein the second polishing unit and the second polishing unit moving means are attached to a second polishing unit holding body including a second horizontal beam in parallel with the first horizontal beam of the first polishing unit holding body, and the second polishing unit holding body is capable of being translated in a horizontal direction with respect to the second horizontal beam. Thus, it is possible to polish the substrate using the first and second polishing units. Further, when the first and second polishing units reach the end portions of the end faces being currently polished, it is possible to simultaneously chamfer corner portions of the substrate by setting the moving direction of each of the polishing units appropriately. Further, it is possible to easily make the chamfering of the corner portion of the substrate correspond to either C-face chamfering or round chamfering.

The table rotating mechanism has a structure of rotating the center table such that the substrate mounted on the center table is put in a state of being rotated by a predetermined angle of 30 to 60 degrees with respect to the reference state, and the first polishing unit and the second polishing unit have a structure for simultaneously polishing the end faces facing each other of the substrate held on the rotated center table, respectively. Thus, it is possible to perform polishing at a high efficiency without the first and second polishing units interfering with each other.

A polishing apparatus according to the present invention includes: a table unit, having a substrate mounted thereon, for fixedly holding the substrate in a predetermined reference state; four polishing units each including a polishing grind stone for polishing one of four respective end faces of the substrate held on the table unit and substrate side edge portion supporting means for supporting respective lower face of a side edge portion of the substrate in a vicinity of the respective end face of the substrate to be polished by the respective grind stone; four unit moving means each, together with the respective substrate side edge portion supporting means, for moving the respective polishing unit along the respective end face of the substrate while each polishing grind stone is polishing the respective end face of the substrate; and four polishing unit transfer mechanism each for moving the respective polishing unit in a direction closer to or away from the respective end face of the substrate. Thus, it is possible to stably and simultaneously polish four end faces of the substrate using the four respective polishing units at a high precision without sustaining any influence of a displacement in the thickness direction of the substrate.

An image capturing device is provided on each polishing unit, the image capturing device being for capturing an image of an alignment mark provided on the substrate and capturing a polishing site by each polishing grind stone, the polishing apparatus further including: an image processing device for computing image data of the alignment mark and the polishing site obtained from each image capturing device; and a control section for computing a rotation angle with respect to the reference state of the substrate mounted on the center unit based on the positional data of the alignment mark computed by the image processing device and for computing a polishing amount of each end face to control the respective polishing unit transfer mechanism. Thus, it is possible to compute the tilt of the substrate mounted on the table unit, so that the polishing grind stone can be moved along the end face of the substrate to perform polishing at a high precision.

Each polishing unit includes an air blowing device between the image capturing device and the polishing grind stone, respectively, for blowing air on the respective image capturing device. Thus, it is possible to capture an image of the polishing site at a high precision.

A polishing method according to the present invention includes: a holding step of mounting the substrate on the table unit and fixedly holding the substrate in the reference state by the table unit; a supporting step of supporting a side edge portion of the substrate held on the table unit by the substrate side edge portion supporting means of the first polishing unit; and a moving step of moving, while the polishing grind stone of the first polishing unit is polishing the end face of the side edge portion supported by the substrate side edge portion supporting means, the first polishing unit along the end face being polished by the first polishing unit moving means. Thus, it is possible to prevent, by the polishing grind stone, the polishing sites from rising at the time of polishing, and it is also possible to position the polishing sites in order at a high precision, thereby stably performing polishing at a high precision without sustaining any influence of displacement in the thickness direction of the substrate.

The center table includes suction means for suctioning the central portion of the substrate, and in the holding step, the central portion of the substrate is suctioned by the suction means of the center table. Thus, it is possible to prevent a rotation and a positional displacement of the substrate even if a rotating moment is generated at the time of polishing.

The table unit of the polishing apparatus includes a plurality of substrate auxiliary supporting means, the plurality of substrate auxiliary supporting means being arranged around the center table to respectively support side portions of the lower surface of the substrate held on the center table, and in the holding step, a side portion of the lower surface of the substrate fixedly held on the center table is supported by at least one of the plurality of substrate auxiliary supporting means. Thus, if the size of the substrate becomes large, it is possible to prevent the occurrence of an undulation on the substrate by supporting the substrate between the center table and the polishing unit using the substrate auxiliary supporting means.

The substrate auxiliary supporting means of the polishing apparatus includes a sliding mechanism for sliding the auxiliary supporting base closer to or away from the center table, and in the holding step, the substrate auxiliary supporting means is slid to support the side portion of the substrate fixedly held on the center table. Thus, it is possible to stably support the substrate. In addition, there is no need for any change of tools (e.g., change of tables) in order to correspond to substrates of various sizes.

The table unit of the polishing apparatus includes a table rotating mechanism for rotating the center table, and in the holding step, the end face of the substrate is rotated by the rotating mechanism so as to be along the moving direction of the first polishing unit by the first polishing unit moving means. Thus, even if the substrate held on the table unit is rotated in a horizontal direction with respect to a reference position, it is possible correct the posture of the substrate by rotating the table unit such that a processing line for the substrate and the moving direction of a polishing grind stone are parallel to each other.

The first polishing unit and the first polishing unit moving means of the polishing apparatus are attached to a first polishing unit holding body, the first polishing unit holding body having a horizontal beam being arranged along the end face of the substrate held on the table unit, and the first polishing unit holding body is movable in a horizontal direction with respect to the vertical beam, and in the moving step, the first polishing unit is moved by the first polishing unit holding body while the first polishing unit is moved so as to be along the end face of the substrate by the first polishing unit moving means. Thus, it is possible to control such that the polishing grind stone moves along the end face of the substrate.

A polishing method according to the present invention includes: a holding step of mounting the substrate on the table unit and fixedly holding the substrate in the reference state by the table unit; a supporting step of supporting a side portion of the substrate held on the table unit by the substrate side edge portion supporting means of the first polishing unit; and a moving step of moving, while the polishing grind stone of the first polishing unit is polishing the end face of the side edge portion supported by the substrate side edge portion supporting means, the first polishing unit along the end face being polished by the first polishing unit moving means, the method further including the steps of: subsequent to the holding step and prior to the moving step, capturing an alignment mark provided on the substrate held on the table unit by the image capturing device; next, processing image data of the alignment mark by the image capturing device and generating positional data of the alignment mark; and next, computing a rotation angle with respect to the reference state of the substrate based on the positional data of the alignment mark processed by image capturing device, wherein in the moving step, a movement of the first polishing unit holding body is controlled based on the computed rotation angle such that the first polishing unit moves along the end face of the substrate. Thus, it is possible to compute the tilt of the substrate mounted on the center table or the table unit in a horizontal direction with respect to the reference state and control the polishing grind stone to move along the end face of the substrate.

Further, a polishing method according to the present invention includes: a holding step of mounting the substrate on the table unit and fixedly holding the substrate in the reference state by the table unit; next, a rotating step of rotating the table unit by a predetermined angle with respect to the reference state of the substrate by the table rotating mechanism; a supporting step of supporting side edge portions facing each other of the substrate held on the table unit by the respective substrate side edge portion supporting means of the first polishing unit and the second polishing unit; and a moving step of moving, while the polishing grind stones of the first polishing unit and the second polishing unit are polishing the respective end faces of the side edge portions supported by the respective substrate side edge portion supporting means, the first polishing unit and the second polishing unit along the respective end faces being polished by the first polishing unit moving means and the first polishing unit holding body and the second polishing unit moving means and the second polishing unit holding body. Thus, it is possible to assuringly avoid interference between the first and second polishing units and it is also possible to shorten the waiting time for the completion of polishing. Further, when the polishing unit reaches an end portion of the end face being currently polished, it is possible to simultaneously chamfer a corner portion of the substrate by setting the moving direction of the polishing unit appropriately. Further, it is possible to easily make the chamfering of the corner portion of the substrate correspond to either C-face chamfering or round chamfering.

The predetermined angle is an angle having a range of 30 degrees to 60 degrees with respect to the reference state. Thus, when the predetermined angle of the table is set in advance as 30 degrees, 45 degrees or 60 degrees, which is easy for performing a computation, it is possible to compute the moving direction of the polishing grind stone of the polishing unit. Therefore, it is possible to shorten the waiting time for the completion of polishing.

Further, a polishing method according to the present invention includes: a holding step of mounting the substrate on the table unit and fixedly holding the substrate in the reference state by the table unit; and a supporting step of supporting side edge portions of the substrate held on the table unit by the respective substrate side edge portion supporting means of the four first polishing units; a moving step of moving, while the polishing grind stones of the polishing units are polishing the respective end faces of the side edge portions supported by the respective substrate side edge portion supporting means, the first polishing units along the respective end faces being polished by the respective polishing unit moving means. Thus, it is possible to stably and simultaneously polish four end faces of the substrate by the four respective polishing units and it is also possible to position in order and polish the polishing sites of the respective end faces of the substrate at a predetermined position at a high precision, without sustaining any influence of a displacement in the thickness direction of the substrate.

In the moving step, the method computes the amount of polishing of each end face based on the image data of the respective polishing sites obtained from the respective image capturing device and controls the respective polishing unit transfer mechanism. Thus, it is possible to always produce a constant amount of polishing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view schematically showing a structure of a polishing apparatus according to an embodiment of the present invention.

FIG. 2 is a side view schematically showing an essential structure of a polishing unit used in the polishing apparatus.

FIG. 3 is a front view showing an essential structure of the polishing unit.

FIG. 4 is a cross-sectional view of a polishing grind stone used in the polishing unit.

Portions (A) and (B) of FIG. 5 respectively show a partially-broken side view showing a structure of a free bearing used in the polishing unit.

FIG. 6 is a plan view showing a structure of a table unit used in the polishing apparatus according to Embodiment 1.

FIG. 7 is a side view showing a structure of a slide base in the table unit.

FIG. 8 is a side view for explaining a waiting state of the polishing unit according to the present invention.

FIG. 9 is a side view for explaining a processing state of the first polishing unit according to the present invention.

FIG. 10 is a side view for explaining another example of an initial state of the first polishing unit according to the present invention.

FIG. 11 is a side view for explaining still another example of the waiting state of the first polishing unit according to the present invention.

FIG. 12 is a side view for explaining another example of the processing state of the first polishing unit according to the present invention.

FIG. 13 is a side view showing an essential structure of a second polishing unit for an end face of the substrate used in the polishing apparatus according to the present invention.

FIG. 14 is a front view showing an essential structure of the second polishing unit according to the present invention.

FIG. 15 is a side view for explaining a waiting state of the second polishing unit according to the present invention.

FIG. 16 is a side view for explaining a processing state of the second polishing unit according to the present invention.

FIG. 17 is an explanatory diagram showing a first polishing work for an end face of the substrate using the polishing apparatus according to Embodiment 1.

FIG. 18 is an explanatory diagram showing a second polishing work for an end face of the substrate using the polishing apparatus according to Embodiment 1.

FIG. 19 is an explanatory diagram showing a third polishing work for an end face of the substrate using the polishing apparatus according to Embodiment 1.

FIG. 20 is a perspective view showing the appearance of a polishing apparatus for an end face of a substrate according to Embodiment 2 of the present invention.

FIG. 21 is an explanatory diagram showing a polishing work for an end face of the substrate using the polishing apparatus according to Embodiment 2.

FIG. 22 is a plan view schematically showing a structure of a polishing apparatus for an end face of a substrate according to Embodiment 3 of the present invention.

FIG. 23 is a plan view showing a structure of an end portion of a liquid crystal display unit.

FIG. 24 is a side view showing a structure of an end portion of a liquid crystal display unit.

FIG. 25 is a perspective view showing the liquid crystal display unit for explaining the processing of the liquid crystal display unit.

FIG. 26 is a side view for explaining an essential structure of a conventional polishing apparatus for an end face of the substrate.

FIG. 27 is a diagram for explaining an operation of the polishing apparatus.

-   -   30, 80A, 80B, 90 polishing apparatus     -   31, 40 a, 40 aA, 40 aa, 40 b, 91 polishing unit     -   32 table     -   33 substrate     -   33 a end face     -   34, 46 spindle motor     -   35, 45 polishing grind stone set     -   36, 41 polishing head     -   37, 49, 49A, 49B image capturing device     -   38, 44 polishing head moving mechanism     -   42, 42A, 42B substrate side edge portion supporting means     -   42 b, 52 a opening portion     -   42 a supporting plate portion     -   43, 84 LM guide     -   43 a LM block     -   43 b LM rail     -   45 i polishing grind stone     -   45 ia tapered portion     -   45 ib flat portion     -   47 servo motor     -   48 ball screw unit     -   48 a screw shaft     -   48 b nut portion     -   50, 50A, 50B, 65 free bearing     -   50 a large ball     -   50 b small ball     -   50 c bearing body     -   50 d cap     -   50 e flange portion     -   50 f of bolt     -   51 vertical base plate     -   52 horizontal base plate     -   53 cylinder     -   54 piston rod     -   57 upward-and-downward plate     -   60 table unit     -   61 center table     -   61 a, 61 b suction groove     -   62 a first auxiliary supporting base     -   63 a second auxiliary supporting base     -   63 b second upward-and-downward air cylinder     -   63 c bearing     -   63 d second guide rod     -   63 g sliding motor     -   63 h second slide base     -   63 i guide rail     -   63 j second guide body     -   63 l rack     -   63 m second pinion     -   64 fixing base     -   81A, 81B polishing unit holding body moving mechanism     -   82 base mount     -   83A, 83B polishing unit holding body     -   85A, 85B polishing unit moving mechanism     -   92 moving guide body     -   96 air blowing device

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1

FIG. 1 is a perspective view schematically showing a structure of a polishing apparatus according to Embodiment 1 of the present invention. This polishing apparatus 80A includes: a base mount 82; a table unit 60 provided on the base mount 82 such that a substrate, an end face of which is to be polished, is held; a polishing unit 40 a for polishing the end face of the substrate held on the table unit 60; a polishing unit holding body 83A for holding the polishing unit 40 a; a pair of LM guides 84 for guiding the polishing unit holding body 83A; a polishing unit holding body moving mechanism 81A for moving the polishing unit holding body 83A along the pair of LM guides 84; a polishing unit moving mechanism 85A for moving the polishing unit 40 a held on the polishing unit holding body 83A; an image capturing device 49A attached to the polishing unit 40 a; a control section 88 and an image processing device 89.

The upper surface of the base mount 82 is horizontal and has a rectangular shape. In the following description, the direction having the shorter side of the upper surface of the base mount 82 is defined as the X-axis direction, the direction having the longer side is defined as the Y-axis direction and the vertical direction is defined as the Z-axis direction. The table unit 60 is provided at the central portion of the upper surface of the base mount 82, the table unit 60 holding in a horizontal state a substrate (not shown) targeted for processing, which has been provided thereon. The table unit 60 can rotate in the horizontal state the held substrate by an arbitrary angle. The pair of LM guides 84 extending along the Y-axis direction is provided on respective upper side portions of the base mount 82 along the Y-axis direction, the upper side portions being located at both sides of the table unit 60 in the X-axis direction.

Legs of the polishing unit holding body 83A are provided on the pair of the LM guides 84 so as to be movable along the respective LM guides 84, the legs having the shape of a gate. The polishing unit holding body 83A is structured to have the shape of the gate in which the upper end portions of the legs are connected to each other by a horizontal beam. The horizontal beam passes over the table unit 60 when the polishing supporting body 83A is moved along the pair of LM guides 84.

The polishing unit holding body moving mechanism 81A is provided on the base mount 82 in order to move in both directions along in the Y-axis the legs of the polishing unit holding body 83A along the pair of LM guides 84, respectively. The polishing unit 40 a is held on the horizontal beam of the polishing unit holding body 83A so as to be movable in the X-axis direction, the polishing unit 40 a polishing an end face of the substrate held on the table unit 60. The polishing unit 40 a is moved in both directions the X-axis direction by the polishing unit moving mechanism 85A along the horizontal beam of the polishing unit holding body 83A.

The image capturing device 49A is provided on the polishing unit 40 a in order to capture a pair of alignment marks provided on the substrate, which is held on the table unit 60. The image capturing device 49A is structured by a CCD camera or the like and captures the alignment marks provided on the substrate and it also captures the polishing site of the substrate. Image data obtained by the image capturing device 49A is image-processed by the image processing device 89. The data image-processed by the image processing device 89 is then output to the control section 88. The control section 88 controls the operation of the entire polishing apparatus 80 and computes the tilt with respect to the X-axis and Y-axis directions on the horizontal surface of the substrate mounted on the table unit 60 based on the image-processed data from the image processing device 89 and stores the result thereof in a memory.

The polishing unit 40 a, which is movable in the X-axis direction by the polishing unit moving mechanism 85A, is moved in the Y-axis direction when the polishing unit holding body 83A is moved in the Y-axis direction by the polishing unit holding body moving mechanism 81A. The polishing unit holding body moving mechanism 81A includes a ball screw (not shown) and a servo motor (not shown). The gate-shaped legs of the polishing unit holding body 83A are moved in both directions along the Y-axis along the pair of LM guides 84 provided on the base mount 82 due to forward rotation and reverse rotation of the ball screw by the servo motor. The polishing unit holding moving mechanism 81A is not limited to the structure of a ball screw and a servo motor, but it can have a structure of a linear motor and the like.

The polishing unit moving mechanism 85A for moving in the X-axis direction the polishing unit 40 a, which is held so as to be movable along the side surface of the horizontal beam of the polishing unit holding body 83A, is structured by a ball screw, a servo motor, an LM guide and the like. The polishing unit 40 a is moved in both directions along the X-axis due to forward rotation and reverse rotation of the screw ball by the servo motor. The polishing unit moving mechanism 85A is not limited to the structure of a ball screw and a servo motor, but it can have a structure of a linear motor and the like.

The polishing unit 40 a which is supported on the polishing unit holding body 83A of the polishing apparatus 80A will be described with reference to FIG. 2 and FIG. 3. FIG. 2 is a side view of the polishing unit 40 a in the X-axis direction (arrow A direction in FIG. 1). FIG. 3 is a front view of the polishing unit 40 a in the Y-axis direction (arrow B direction in FIG. 1). FIG. 2 and FIG. 3 also show the relationship with respect to X-Y-Z axis of FIG. 1. In FIG. 2 and FIG. 3, the polishing unit 40 a includes: a polishing head 41 capable of moving in the up-down direction; a substrate side edge portion supporting means 42 capable of moving in the up-down direction and being fixed at a predetermined height; a pair of moving guides (LM guides) 43; a polishing head moving mechanism 44 for moving the polishing head 41 in Z-axis (vertical) direction. The image capturing device 49A (see FIG. 1) provided on the polishing unit 40 a is not shown in FIG. 2 and FIG. 3.

The polishing head 41 is attached to a vertical base plate 51, which is supported in a vertical state and is slidable in the X-axis direction along the horizontal beam of the polishing unit holding body 83A. The polishing head 41 includes a spindle motor 46, which is supported so as to be movable in the up-down direction (Z-axis direction) along the vertical base plate 51. A rotation axis of the spindle motor 46 is arranged along Z-axis (vertical) direction and the rotation axis is also arranged so as to protrude downward. At the bottom portion of the rotation axis, a polishing grind stone set 45 in the shape of cylinder is attached so as to be forwardly rotated and reversely rotated by the spindle motor 46. The forward rotation and the reverse rotation of the polishing grind stone set 45 by the spindle motor 46 are selected depending on the processing condition.

The polishing head 41 is held so as to be slidable in the Z-axis direction (up-down direction) by the pair of LM guides 43, which is provided on the vertical base plate 51, and is moved in the Z-axis direction by the polishing head moving mechanism 44 and is positioned at a high precision. Each of the pair of LM guides 43 includes an LM rail 43 b which is arranged along the Z-axis direction as shown in FIG. 3. The pair of LM rails 43 b is provided in the X-axis direction in parallel to each other with an appropriate gap therebetween. On each of the LM rails 43 b, a pair of upper and lower LM blocks 43 a is provided to be slidable in the Z-axis direction. The pair of upper and lower LM blocks 43 a is respectively attached to left and right side portions of the spindle motor 46 at upper and lower positions. The pair of LM rails 43 b is respectively arranged on the left and right sides having the position of the rotation axis of the spindle motor 46 in the X-axis direction and a vertical axis matching the position in the X-axis direction as their center. The spindle motor 46 is held on the pair of LM rails 43 b with high rigidity and is stably guided along the pair of LM rails 43 b in the up-down direction.

The polishing head moving mechanism 44 for moving in the up-down direction the polishing head 41 including the spindle motor 46 and the polishing grind stone set 45 includes a servo motor 47 and one ball screw unit 48. The ball screw unit 48 includes: a screw shaft 48 a arranged at the center of the pair of LM rails 43 b in the left and right direction along the Z-axis direction as shown in FIG. 3; and a nut portion 48 b screw-connected to the screw shaft 48 a as shown in FIG. 2. The nut portion 48 b is integrated to the spindle motor 46 of the polishing head 41 such that it does not rotate. The upper end of the screw shaft 48 a is connected to the servo motor 47. The screw shaft 48 a forwardly rotates and reversely rotates due to forward rotation and reverse rotation of the servo motor 47, and the nut portion 48 b is slid upward and downward along the screw shaft 48 a. Accordingly, the spindle motor 46 is moved upward and downward along the screw shaft 48 a, and thus the entire polishing head 41 is moved along the Z-axis direction. When rotation of the servo motor 47 is stopped, the polishing head 41 is positioned at a predetermined position in the Z-axis direction.

The polishing grind stone set 45 has a similar structure to that of the polishing grind stone set 35 shown in FIG. 26. In the polishing grind stone set 45, “n” number of polishing grind stones 45 i (i=1, 2, . . . , n) each having the shape of substantially disc are concentrically stacked in multiple layers in the up-down direction. FIG. 4 shows a cross-sectional view of one polishing grind stone 45 i. The polishing grind stone 45 i has a V-shaped groove portion 45 ic in the up-down direction at the central portion of an outer circumference thereof. Upper and lower side surfaces of the groove portion 45 ic have tapered portions 45 ia, respectively. The bottom surface of the central portion of the groove portion 45 ic, which is located between the upper and lower tapered portions 45 ia, is a plane flat portion 45 ib. The polishing grind stone 45 i can polish and chamfer upper and lower edges of an end face of a substrate simultaneously owing to the respective tapered portions 45 ia of the V-shaped groove portion 45 ic. In addition, the polishing grind stone 45 i can polish the end face of the substrate simultaneous with the upper and lower edges owing to the flat portion 45 ib of the groove portion 45 ic.

The shape of the groove portion 45 ic of the polishing grind stone 45 i is formed by tooling and dressing. The shape of the groove portion 45 ic of the polishing grind stone 45 i is not limited this. The shape of the groove portion 45 ic may be U-shaped in which each tapered portion 45 ia has a curved surface. Alternatively, the shape of the groove portion 45 ic may be complex such that the polishing grind stone 45 i can chamfer substrates of a bonded substrate at once. The tapered portions 45 ia facing each other can be tilted such that tilted angles thereof with respect to a rotation axis of the polishing grind stone 45 i are different from each other, so that the polishing grind stone 45 i can remove a short-circuit electrode of an electrode terminal of a substrate by polishing. Further, the rotation axis of the polishing grind stone set 45 can be tilted.

It should be noted that an air blowing device (not shown) is provided between the polishing grind stone set 45 and the image capturing device 49A in order to remove polishing powder using air in a predetermined direction, the polishing powder being generated when a substrate is polished. This air blowing apparatus can prevent working fluid from splashing onto the image capturing device 49A.

As shown in FIG. 2 and FIG. 3, a horizontal base plate 52 is attached to the bottom end portion of the vertical base plate 51, to which the polishing head 41 is attached. The horizontal base plate 52 is supported on the lower end surface of the vertical base plate 51 so as to be horizontal below the polishing grind stone set 45 which has been slid upward. An opening portion 52 a having an inner diameter larger than an outer diameter of the polishing grind stones 45 i of the polishing grind stone set 45 is provided in the horizontal base plate 52 such that the polishing grind stone set 45 to be moved downward can pass though the horizontal base plate 52. The opening portion 52 a is penetrated in the up-down direction.

A substrate side edge portion supporting means 42 is provided below the horizontal base plate 52. Once a substrate, an end face of which is to be chamfered, is mounted on the table unit 60, the substrate side edge portion supporting means 42 supports a side edge portion of the substrate such that the side edge is slidable. When the end face of the substrate mounted on the table unit 60 is positioned within a processing range of the polishing grind stone set 45, the substrate side edge portion supporting means 42 supports the side edge portion of the substrate in a horizontal state and adjusts the tilt and the height of the side edge portion of the substrate in order to suppress the downward bending of the side edge portion in the vicinity of the end face including the end face of the substrate. Accordingly, polishing of the end face of the substrate by the polishing grind stones 45 i of the polishing grind stone set 45 is adjusted to have an optimal state.

The substrate side edge portion supporting means 42 includes a supporting plate portion 42 a, which is arranged in a horizontal state below the horizontal base plate 52. The supporting plate portion 42 a can be translated in a horizontal state in the Z-axis direction (vertical direction) by a cylinder 53, which is arranged on the horizontal base plate 52 in the vicinity of the vertical base plate 51. The cylinder 53 is arranged on the horizontal base plate 52 such that a piston rod 54 protrudes downward. The piston rod 54 is penetrated through an opening portion provided in the horizontal base plate 52 and is attached to the supporting plate portion 42 a. The supporting plate portion 42 a is moved in the Z-axis direction by the cylinder 53, and is positioned accordingly at a processing position above and at a waiting position below. As such, the cylinder 53 is a substrate side edge portion supporting means moving mechanism for moving the supporting plate portion 42 a of the substrate side edge portion supporting means 42 in the Z-axis direction.

The piston rod 54 of the cylinder 53 is arranged, as shown in FIG. 2 in the vicinity of the vertical base plate 51 by distance L1 away from the central axis of the rotation axis of the polishing grind stone set 45.

At the central portion of the supporting plate portion 42 a, an opening portion 42 b is provided facing the opening portion 52 a provided on the horizontal base plate 52. The size of the opening portion 42 b of the supporting plate portion 42 a is the same as that of the opening portion 52 a provided in the horizontal base plate 52.

On the upper surface of the supporting plate portion 42 a around the opening portion 42 b, a plurality of free bearings 50 is provided in order to slidably support a side edge portion of a substrate. In an example shown in FIG. 2 and FIG. 3, twelve free bearings 50 are attached in the shape of square (four free bearings 50 are provided on each side) to surround the opening portion 42 b of the supporting plate portion 42 a, for example.

The free bearing 50 is also called ball transfer. The free bearing 50 supports an object to be transferred such that the object can slide in an arbitrary direction (360 degrees) by a spherical body. FIG. 5 is a partial cross-sectional view showing a structure of the free bearing provided on the substrate side edge portion supporting means 42, shown in FIG. 2 and FIG. 3. In this free bearing 50, a concave portion having a semi-spherical shape is provided at the upper portion of a bearing body 50 c. In this semi-spherical concave portion, a plurality of small balls 50 b is accommodated and also a large ball 50 a is accommodated wherein the bottom portion of the large ball 50 a is supported such that it can be rolled by the plurality of small balls 50 b. The upper portion of the large ball 50 a is protruding upward from the concave portion of the bearing body 50 c. The bearing body 50 c is covered by a cap 50 d. The upper portion of the large ball 50 a is protruding from an opening portion provided in the cap 50 d. The large ball 50 a is held by the cap 50 d such that the large ball 50 a cannot be separated from the bearing body 50 c. At a circumferential portion of the cap 50 d, a flange portion 50 e is provided. The flange portion 50 e is fixed to the supporting plate portion 42 a by a screw or the like.

The free bearing 50 is not limited to one having the structure shown in Portion (A) of FIG. 5. However, as show in Portion (B) of FIG. 5, instead of the flange portion 50 e, a free bearing 50B having a structure of a bolt 50 f attached to the bearing body 50 c can be used. In this case, the bolt 50 f is directly attached to the supporting plate portion 42 a.

In any case, a spherical body thereof made by, for example, steel or stainless metal or resin and coated by resin having a low friction coefficient is used as the large ball 50 a.

The plurality of free bearings 50 at the substrate side edge portion supporting means 42 supports a substrate while the crest of each of the large balls 50 a located at the uppermost portion of each of the large balls 50 a contacts the lower surface of the substrate. Therefore, when the crest of each of the large balls 50 a located at the uppermost portion of each of the large balls 50 a of the respective free bearings 50 is adjusted to the same height as that of a surface of the table unit 60 where the substrate is mounted, the side edge portion of the substrate is supported by the plurality of free bearing 50 at the same height as the mounting surface of the table unit 60, thereby preventing the downward bending of the side edge portion of the substrate.

As described later, the polishing head 41 moves along the end face of the substrate mounted on the table unit 60 in a fixed state, and the substrate side edge portion supporting means 42 moves together with the polishing head 41 in an integrated manner while supporting the side edge portion in the vicinity of the end face of the substrate. Since the free bearings 50 are provided on the supporting plate portion 42 a, the side edge portion of the substrate is supported to be slidable by the free bearings 50. As such, the side edge portion of the substrate is supported without sustaining any damages to the lower surface of the substrate.

As a member on the substrate side edge portion supporting means 42 of directly contacting and supporting the lower surface of the substrate, not only is the structure of providing the free bearings 50 on the supporting plate portion 42 a used, but a structure of providing on the supporting plate portion 42 a a supporting member structured by a material having a low friction coefficient (e.g., fluoresin (registered trademark “Teflon”)) can also be used. Alternatively, a structure of the upper surface of the supporting plate portion 42 a coated with a material having a low friction coefficient can be used. With the use of the material having a low friction coefficient (e.g., fluoresin and the like), the substrate can be supported to slide smoothly without causing any damages to the lower surface of the substrate.

Since the spherical large ball 50 a of the free bearing 50 contacts the lower surface of the side edge portion of the substrate, polishing powder is less likely to adhere to the surface of the large ball 50 a, thereby preventing the substrate from sustaining any damages due to the polishing powder. Since the large ball 50 a of the free bearing 50 point-contacts the lower surface of the substrate and moreover the large ball 50 a itself is rotatable, the friction resistance thereof is small and further there is no concern of limiting the moving direction of the substrate, thereby supporting the substrate to slide smoothly without causing any damages to the side edge portion of the substrate. As a result, the polishing unit 41 can perform polishing while the side edge portion of the substrate in the vicinity of a site to be polished is supported by the substrate side edge portion supporting means 42. Thus, it is possible to polish an end face of the substrate at a high precision while accurately performing the positioning of the substrate in the height direction thereof such that no undulation, bending, or the like of the substrate occurs.

Next, the table unit 60 for fixing the substrate targeted for processing will be described. FIG. 6 is a plan view showing a structure of the table unit 60 used in the polishing apparatus according to the present invention. The table unit 60 includes: a square-shaped center table 61 for holding the central portion of a substrate by vacuum suction; and four substrate auxiliary supporting means 67 provided around the center table 61.

Once the central portion of the substrate is mounted on the center table 61, the center table 61 suctions and fixedly holds the central portion of the mounted substrate. When the coordinates of the central position S of the center table 61 are denoted as (X0, Y0, Z0), the square-shaped center table 61 is arranged in a horizontal state along the X-axis direction and the Y-axis direction and is rotatable about Z-axis as its center without moving in any direction of X-axis, Y-axis and Z-axis.

The center table 61 is connected to a rotating table (not shown) of a rotating mechanism, which is provided below a fixing base 64 (see FIG. 7) on the upper surface of the base mount 82 and the center table 61 is rotated by this rotating mechanism. The rotating mechanism can rotate the center table 61 by very small degrees in a horizontal state. The rotating mechanism is structured by a servo motor or the like which is controlled by the control section 88.

In order to suction and hold the central portion of the lower surface of the substrate, a first suction groove 61 a having a square-shape, which is of the same shape of the center table 61, and a second suction groove 61 b having a cross shape with the central position (X0, Y0, Z0) of the center table 61 as its center are provided on the upper surface of the center table 61. The second suction groove 61 b is formed by a pair of straight lines along the X-axis direction and the Y-axis direction, respectively. End portions of each straight line are positioned approximately in the middle between the central position (X0, Y0, Z0) of the center table 61 and respective side edges making up an outer circumference of the center table 61. Straight groove portions of the first suction groove 61 a extending along the respective side edges of the center table 61 are formed approximately in the middle between the end portions of the straight lines making up the second suction groove 61 b and the respective side edges of the center table 61.

The interior of each of the first suction groove 61 a and the second suction groove 61 b is depressurized by a vacuum pump (not shown). The substrate mounted on the center table 61 is suctioned to the depressurized interior of each of the first suction groove 61 a and the second suction groove 61 b. Thus, the substrate is fixedly held on the center table 61.

In the case that a substrate is mounted on the center table 61 and an end face of the substrate is processed, when a rotating polishing grind stone 45 i of the polishing grind stone set 45 contacts the end face of the substrate, a rotating moment is generated on the substrate. However, the first suction groove 61 a and the second suction groove 61 b of the center table 61 vacuum-suction and fixedly support the central portion of the substrate, thereby assuringly preventing the substrate from rotating and moving, which will result in a displacement thereof from a predetermined position on the center table 61.

The four substrate auxiliary supporting mechanisms 67 arranged around the center table 61 have the same structure to each other and have first auxiliary supporting bases 62 a in the strip shape arranged along the respective side edges of the square-shaped center table 61 and second auxiliary supporting bases 63 a in the strip shape arranged along the respective first auxiliary supporting bases 62 a outside the first auxiliary supporting bases 62 a.

FIG. 7 is a side view of the substrate auxiliary supporting mechanism 67 from the −X-axis direction located in the −X-axis direction with respect to the central position of the central table 61 shown in FIG. 6. As shown in FIG. 7, below the second auxiliary supporting base 63 a, a second slide base 63 h is arranged below the second auxiliary supporting base 63 a in a horizontal state facing the second auxiliary supporting base 63 a. The second slide base 63 h supports the second auxiliary supporting base 63 a such that the second auxiliary supporting base 63 a is slidable in the Z-axis direction (up-down direction) and the second slide base 63 h is also slidable along the X-axis direction and the Y-axis direction so as to be closer to and away from the center table 61.

Similarly, below the first auxiliary supporting base 62 a, a first slide base 62 h (see FIG. 6) arranged in a horizontal state facing the first auxiliary supporting base 62 a is provided. In FIG. 6, the substrate auxiliary supporting mechanisms 67 respectively located in the −X-axis direction and the +Y-axis direction with respect to the center table 61 omit the first auxiliary supporting base 62 a and the second auxiliary supporting base 63 a located above and illustrate the first slide base 62 h and the second slide base 63 h located below.

The second slide base 63 h slides along a pair of guide rails 63 i provided on a fixing base 64, which is arranged below the second slide base 63 h, as shown in FIG. 7. The pair of guide rails 63 i is arranged along the X-axis direction and the Y-axis direction, respectively. On the lower surface of the strip-shaped second slide base 63 h, second guide bodies 63 j to engage with the respective guide rails 63 i are attached. The second slide base 63 h is translated in a direction to move closer to and away from the center table 61 when the pair of second guide bodies 63 j slides with respect to the respective guide rails 63 i.

On the second slide base 63 h, a second sliding motor 63 g structured by a servo motor is attached. A rotation axis of the second sliding motor 63 g is protruding below the second slide base 63 h, and a second pinion 63 m is attached to the lower end portion of the rotation axis so as to forwardly rotate and reversely rotate together with the rotation axis in an integrated manner. A sensor is provided on the rotation axis of the second sliding motor 63 g in order to detect a rotation number (rotation angle), and the rotation of the second sliding motor 63 g is controlled by this sensor.

In the vicinity of one of the guide rails 63 i, a rack 63 l is provided in parallel to the guide rail 63 i, and the second pinion 63 m described above engages with the rack 63 l. The second pinion 63 m forwardly and reversely rotated by the second sliding motor 63 g rotates on the rack 63 l to move along the rack 63 l. As a result, the second slide base 63 h, to which the second sliding motor 63 g for causing the second pinion 63 m to rotate is attached, is slid together with the second pinion 63 m.

Similarly, on the lower surface of the first slide base 62 h arranged below the first auxiliary supporting base 62 a, first guide bodies (not shown) respectively engaging with the pair of guide rails 63 i are provided. As shown in FIG. 6, a first sliding motor 62 g is provided on the first slide base 62 h, and a first pinion 62 m engaged with the rack 63 l is attached to the lower end portion of a rotation axis of the first sliding motor 62 g. Accordingly, the first slide base 62 h is translated along the pair of the guide rails 63 i to move closer to and away from the center table 61 due to forward rotation and reverse rotation of the first sliding motor 62 g.

As shown in FIG. 7, a second upward-and-downward air cylinder 63 b is provided at the central portion of the second slide base 63 h on the upper surface of the second slide base 63 h in order to move the second auxiliary supporting base 63 a upward and downward. The second upward-and-downward air cylinder 63 b is arranged in a vertical state such that a piston rod slides in the up-down direction. The upper end portion of the piston rod is attached to the central portion of the second auxiliary supporting base 63 a at the lower surface of the second auxiliary supporting base 63 a arranged in a horizontal state.

On both sides of the lower surface of the second auxiliary supporting base 63 a, upper end portions of second guide rods 63 d respectively arranged in a vertical state are attached. The second guide rods 63 d are supported by bearings 63 c respectively provided on the upper surface of the second slide base 63 h so as to be slidable in the up-down direction.

Owing to such a structure, the second auxiliary supporting base 63 a is moved upward and downward by the second upward-and-downward air cylinder 63 b while maintaining the horizontal state with respect to the second slide base 63 h. The second auxiliary supporting base 63 a is moved upward to a working position (Z-axis coordinate=Z0), which is the same height as the upper surface of the center table 61, and is positioned at the working position. Also, the second auxiliary supporting base 63 a is moved downward to a waiting position, which is lower than the working position by height L3 and is positioned at the waiting position.

As shown in FIG. 6, similarly, at the central portion of the first slide base 62 h at the upper surface of the first slide base 62 h, a first upward-and-downward air cylinder 62 b is provided in order to move the first auxiliary supporting base 62 a upward and downward. The first upward-and-downward air cylinder 62 b is arranged in a vertical state such that a piston rod slides in the up-down direction. The upper end portion of the piston rod is attached to the central portion of the first auxiliary supporting base 62 a at the lower surface of the first auxiliary supporting base 62 a arranged in a horizontal state.

On both sides of the lower surface of the first auxiliary supporting base 63 a, upper end portions of first guide rods 62 d respectively arranged in a vertical state are attached. The first guide rods 62 d are supported by bearings 63 c respectively provided on the upper surface of the first slide base 62 h so as to be slidable in the up-down direction.

Owing to such a structure, similarly, the first auxiliary supporting base 62 a is moved upward and downward by the first upward-and-downward air cylinder 62 b while maintaining the horizontal state with respect to the first slide base 63 h. The first auxiliary supporting base 62 a is moved upward to a working position (Z-axis coordinate=Z0), which is the same height as the upper surface of the center table 61, and is positioned at the working position. Also, the first auxiliary supporting base 62 a is moved downward to a waiting position, which is lower than the working position by height L3 and is positioned at the waiting position.

As shown in FIG. 6 and FIG. 7, a plurality of free bearings 65 is provided on the upper surface of the second auxiliary supporting base 63 a. Each free bearing 65 has a structure similar to that of the free bearing 50 provided on the substrate side edge portion supporting means 42 of the polishing unit 40 a, and the free bearings 50 are provided, for example, in zigzag arrangement on the upper surface of the strip-shaped second auxiliary supporting base 63 a.

Similarly, as shown in FIG. 6, a plurality of free bearings 65 is provided on the upper surface of the first auxiliary supporting base 62 a. Each free bearing 65 has a structure similar to that of the free bearing 50 provided on the substrate side edge portion supporting means 42 of the polishing unit 40 a, and the free bearings 50 are provided, for example, in zigzag arrangement on the upper surface of the strip-shaped second auxiliary supporting base 63 a.

In the table unit 60 having such a structure described above, the central portion of the substrate, an end face of which is to be polished, is mounted on the center table 61. Depending on the size of the substrate to be mounted on the center table 61, a pair of first auxiliary supporting bases 62 a arranged with the center table 61 therebetween or all the first auxiliary supporting bases 62 a are moved to a working position which is of the same height as the upper surface of the center table 61, or alternatively, a pair of second auxiliary supporting bases 63 a arranged with the center table 61 therebetween or all the second auxiliary supporting bases 63 a are moved to the working position which is of the same height as the upper surface of the center table 61 to support the side portions of the substrate mounted on the center table 61.

When the size of a substrate to be mounted on the center table 61 is small and thus there is no need for the side portions to be supported by the first auxiliary supporting base 62 a and the second auxiliary supporting base 63 a, the first auxiliary supporting base 62 a and the second auxiliary supporting base 63 a are moved to the waiting position located below the working position.

The center table 61 is rotatable in a horizontal state, and each substrate auxiliary supporting means 67 arranged around the center table 61 is structured so as to rotate with the center table 61 in an integrated manner.

The free bearings 65 are provided on the first auxiliary supporting base 62 a and the second auxiliary supporting base 63 a. Thus, the free bearings 65 point-contact the lower surface of a substrate, thereby supporting the substrate without causing any damages to the lower surface of the substrate. Instead of the free bearing 65, a substrate supporting member structured by a material having a low friction coefficient can be provided. Alternatively, instead of providing the free bearing 65 or the like, suction grooves are provided in the first auxiliary supporting base 62 a and the second auxiliary supporting base 63 a, as are provided in the center table 61, to fixedly support side portions of a substrate.

A mechanism for moving each of the first auxiliary supporting base 62 a and the second auxiliary supporting base 63 a is structured such that working fluid used at the time of polishing a substrate does not enter the mechanism.

The operation of the polishing apparatus structured as described above will be described. FIG. 8 is an explanatory diagram showing an initial state when the end face 33 a of the small-sized substrate 33 is chamfered while the substrate 33 is mounted on the center table 61. In the case of the small-sized substrate 33, only the center table 61 of the table unit 60 is used to hold the substrate 33. FIG. 8 shows only the minimum number of elements which are required to describe the polishing work of the polishing apparatus 80.

When the substrate 33 is mounted on the center table 61, the interior of each of the first suction groove 61 a and the second suction groove 61 b provided on the upper surface of the center table 61 is depressurized, and thus the substrate 33 is suctioned to the center table 61 and fixedly held on the center table 61.

Thereafter, the polishing unit holding body 83A is moved in the Y-axis direction by the polishing unit holding body moving mechanism 81A to move closer to the center table 61, and side portions of the center table 61 on the substrate side edge portion supporting means 82 are positioned below the substrate fixed to the center table 61. In this case, the end face of the substrate 33 is put in a state of being adjacent to the polishing grind stone set 45 of the polishing unit 40 a.

In this state, the polishing head 41 including the polishing grind stone set 45 and the spindle motor 46 is positioned by the polishing head moving mechanism 44 shown in FIG. 2 such that polishing reference position P2, which is the central position of the lower surface of a polishing grind stone 45 i of the polishing grind stone set 45 to be used, is positioned at approximately the same height at the upper surface of the center table 61. The substrate side edge portion supporting means 42 of the polishing unit 40 a is positioned, by the operation of the cylinder 53, at a waiting position, which is lower than the polishing reference position by a predetermined height L2. Normally, polishing grind stones 45 i are used in order, starting with the polishing grind stone 45 i which is located at the lowest layer of the polishing grind stone set 45. Therefore, at the start of the polishing work, the central position at the lower surface of the polishing grind stone set 45 at the lowest layer is recognized as the polishing reference position P2.

In this case, the substrate side edge portion supporting means 42 is moved downward such that the substrate side edge portion supporting means 42 is positioned at the reference position P1, which is below the polishing reference position P2 of the substrate side edge portion supporting means 42. The reference position P1 has the same X coordinate and Y coordinate as those of the polishing reference position P2, and the reference position P1 is positioned at the same height as the crest of the free bearings provided on the substrate side edge portion supporting means 42.

When X coordinate and Y coordinate of the polishing reference position P2 and the reference position P1 are denoted as X1 and Y1, respectively, the coordinates of the polishing reference position P2 are (X1, Y1, Z0), and the reference position P1 is a waiting position having the coordinates (X1, Y1, Z0-L2), since the coordinates of the central position S of the center table 61 are (X0, Y0, Z0). Thus, the cylinder 53 moves the substrate side edge portion supporting means 42 downward such that the reference position P1 of the substrate side edge portion means 42 is positioned lower than the polishing reference position P2 by distance L2. Accordingly, the polishing reference position P2 is sufficiently higher than the reference position P1 of the substrate side edge portion supporting means 42.

Thereafter, as shown in FIG. 9, the substrate side edge portion supporting means 42 of the polishing unit 40 a is moved upward by the distance L2 by the operation of the cylinder 53, and at the same time, the polishing head 41 is moved downward by the servo motor 47 of the polishing head moving mechanism 44 such that the reference position P2 of the polishing head 41 is lowered by ΔZ. Accordingly, a side edge portion of the substrate 33, the central portion of which is supported by the center table 61, is supported by the free bearings 50 so as to have the same height as the center table 61, and the part from the central portion of the substrate 33 held on the center table 61 to the side edge portion of the substrate 33 to be polished is put into a horizontal state, as shown in FIG. 9. The end face 33 a of the substrate 33 is adjacent to and faces the side surface of the polishing grind stone 45 i at the lowest layer of the polishing grind stone set 45.

In this state, the image capturing device 49A optically captures two alignment marks provided on the substrate 33. Image data of the alignment marks captured by the image capturing device 49A is processed by the image processing device 89. Thus, the coordinates of the central point (also called center of balance) between the alignment marks are obtained. Next, based on the coordinates of the central point of the two alignment marks, the control section 88 computes the rotation angle (rotation angle about the Z-axis direction in the X-Y plane) θ of the substrate 33 in a horizontal direction with respect to a normal holding position of the substrate 33 at the center table 61, and the control section 88 controls a table unit rotation mechanism such that the computed rotation angle θ is removed. Accordingly, the entire table unit 60 is rotated by θ degrees, and the rotation of the substrate 33 in a horizontal surface is corrected such that the end face 33 a of the substrate 33 mounted on the table unit 60 matches the moving direction of the polishing grind stone set 45 along the X-axis direction. As a result, in a subsequent step of chamfering, it is possible to prevent the change in amount of chamfering of the end face of the substrate 33 mounted on the table unit 60, thereby performing polishing at an extremely high precision regardless of the size of the substrate 33.

Instead of this structure of rotating the substrate 33 in a horizontal direction by the rotation of the table unit 60 to correct the posture of the substrate 33, the angle with respect to the end face 33 a of the substrate 33 in the X-axis direction is computed based on the rotation angle of the substrate 33 in the horizontal direction, which has been obtained from the coordinate values of the two alignment marks, and the control section 88 controls the polishing unit moving mechanism 85A and the polishing unit holding body moving mechanism 81A during polishing, so that the polishing unit 40 is moved along the X-axis direction and is at the same time moved along the Y-axis direction so as to be along the end face 33 a of the substrate 33, which has been rotated in the horizontal direction. Similarly, in this case, it is possible to change the amount of chamfering of the end face 33 a of the substrate 33 even if the substrate 33 held on the center table 61 is not in a normal state, thereby performing polishing at a high precision.

Thereafter, considering the thickness of the substrate 33, the outer diameter, the rotation number and the feeding amount of the polishing grind stone 45 i and the like, the polishing condition of the polishing head 41 is set. The polishing unit holding body 83A is moved in the Y-axis direction by the polishing unit holding body moving mechanism 81A such that the polishing grind stone 45 i at the lowest layer contacts the end face 33 a of the substrate 33 while the polishing grind stone set 45 of the polishing head 41 is being rotated. Accordingly, the end face of the substrate 33 enters into the V-shaped groove portion 45 ic provided in the outer circumference of the polishing grind stone 45 i, and the upper and lower edges of the end face 33 a of the substrate 33 are put into a state of contacting the upper and lower tapered portions 45 ia of the groove portion 45 ic, respectively. As a result, the upper and lower edges of the end face 33 a of the substrate 33 are simultaneously chamfered. When the edges are chamfered, the end face 33 a located between the upper and lower edges are polished by the flat portion 45 ib of the groove portion 45 ic of the polishing grind stone 45 i.

Next, the polishing unit 40 a is moved in the X-axis direction by the polishing unit moving mechanism 85A. As a result, the polishing grind stone 45 i is moved along the end face 33 a of the substrate 33, and the upper and lower edges of the end face 33 a of the substrate 33 are chamfered by the respective tapered portions 45 ia of the polishing grind stone 45 i and at the same time, the end face 33 a is polished.

In this case, the polishing unit 40 a is moved along the end face 33 a of the substrate 33 by the polishing unit moving mechanism 85A, and the substrate side edge portion supporting means 42 is accordingly moved along the end face 33 a of the substrate 33. Thus, the free bearings 50 of the substrate side edge portion supporting means 42 for supporting the vicinity of the end face 33 a of the substrate 33 are smoothly moved while the free bearings 50 are in a state of contacting the lower surface of the substrate 33, thereby stably supporting the vicinity of the end face 33 a of the substrate 33, which is contact with the polishing grind stone 45 i. Therefore, the upper and lower edges of the end face 33 a of the substrate 33 are stably chamfered by the polishing grind stone 45 i.

In order to chamfer one end face 33 a of the substrate 33, an optimal polishing condition is set in consideration of, for example, the thickness of a substrate 33, the outer diameter of each polishing grind stone 45 i of the polishing grind stone set 45, the rotation number and the feeding amount of each polishing grind stone 45 i and the like.

FIG. 10 is an explanatory diagram showing an initial state when the large-sized substrate 33 is chamfered. FIG. 10 shows a state before the substrate is mounted on the center table 61. The polishing unit holding body moving mechanism 81A is moved in the X-axis direction such that the distance from the central position S of the center table 61 of the table unit 60 to the polishing grind stone set 45 is larger than the distance in the state shown in FIG. 8. When the size of the substrate 33, the central portion of which is held on the center table 61, is large and thus, an amount of downward bending of the side edge portion of the substrate 33 is large, a side portion of the substrate 33 is supported by the first auxiliary supporting base 62 of the substrate auxiliary supporting mechanism 67, or by the first auxiliary supporting base 62 and the second auxiliary supporting base 63.

For this, depending on the size of the substrate 33 to be polished, only the first auxiliary supporting base 62, or both the first auxiliary supporting base 62 and the second auxiliary supporting base 63 are moved, by the rotating drive of the first sliding motor 62 g, or the rotating drive of the first sliding motor 62 g and the second sliding motor 63 g, respectively, to the position of a predetermined distance away from the center table 61. The first auxiliary supporting base 62 and the second auxiliary supporting base 63 are moved to a waiting position which has a similar height to that of the substrate side edge portion supporting means 42 of the polishing unit 40 a.

The operation of each of the first auxiliary supporting base 62 and the second auxiliary supporting base 63 is similar to each other. Therefore, only the operation of the second auxiliary supporting base 63 will be described below.

When the second auxiliary supporting base 63 is of a predetermined distance away from the center table 61, the central portion of the substrate 33 is mounted and fixed on the center table 61, as shown in FIG. 11.

Next, in this state, the upward-and-downward air cylinder 63 b is operated, and the second auxiliary supporting base 63 is moved upward and the crest of each of the free bearings 65 provided on the second auxiliary supporting base 63 is moved to the same height as that of the mounting surface of the center table 61. Accordingly, the substrate 33 is supported by the upper surface of the center table 61 and the free bearings 65 of the second auxiliary supporting base 63.

Thereafter, as shown in FIG. 12, the substrate side edge portion supporting means 42 of the polishing unit 40 a is moved upward by height L2 by the cylinder 53, and the polishing head 41 is moved downward by the servo motor 47 of the polishing head moving mechanism 44 such that the height of reference position P2 of the polishing head 41 is lowered by ΔZ.

In this state, thereafter, the end face 33 a of the substrate 33 is polished by an operation similar to that described above.

As described above, a part of the substrate 33, which is located between the center table 61 and the substrate side edge portion supporting means 42 of the polishing head 41, is supported by the first auxiliary supporting base 62 of the substrate auxiliary supporting mechanism 67, or by the first auxiliary supporting base 62 and the second auxiliary supporting base 63. Thus, it is possible to prevent the occurrence of bending of the substrate 33 between the center table 61 and the substrate side edge portion supporting means 42 of the polishing head 41. As a result, it is possible to stably support a side edge portion of the substrate 33 by the substrate side edge portion supporting means 42 even in the case of large-sized substrate 33, thereby performing chamfering of the end face 33 a of the large-sized substrate 33 at a high precision.

When the size of the substrate 33 to be polished is not large and thus there is no need for support of the substrate 33 between the center table 61 and the substrate side edge portion supporting means 42 of the polishing head 41, the first auxiliary supporting base 62 and the second auxiliary supporting base 63 are lowered to the waiting position. As a result, it is possible to perform polishing of the end face 33 a of substrates 33 a of various sizes without any change of tools (e.g., change of tables).

The entire table unit 60 including the center table 61 and the substrate auxiliary supporting mechanism 67 is rotated by a table rotating mechanism while the substrate 33 is mounted. Therefore, when the substrate is held on the center table 61 and the substrate auxiliary supporting mechanism 67 of the table unit 60, there is no concern that the displacement of the substrate 33 with respect to the table unit 60 will occur even if the center table 61 and the substrate auxiliary supporting mechanism 67 are rotated. Since the free bearings 65 for point-contacting the lower surface of the substrate 33 is provided on the first auxiliary supporting base 62 and the second auxiliary supporting base 63 of the substrate auxiliary supporting mechanism 67, there is no concern of causing any damages to the lower surface of the substrate 33 even when the substrate 33 slides at the time of the rotation of the table unit 60.

It is possible to have a structure for rotating only the center table 61 by the table rotating mechanism. Even in this case, there is no concern that the displacement of the substrate 33 will occur since the substrate 33 is fixed on the center table 61. In addition, since the free bearings 65 for point-contacting the lower surface of the substrate 33 is provided on the first auxiliary supporting base 62 and the second auxiliary supporting base 63 of the substrate auxiliary supporting mechanism 67, there is no concern of causing any damages to the lower surface of the substrate 33 even if only the center table 61 is rotated. The table rotating mechanism only has to rotate the center table if the center table 61 is the only element required to be rotated. Thus, a structure of the polishing apparatus can be extremely simplified.

Instead of the structure of attaching the free bearings 65 to both the first auxiliary supporting base 62 and the second auxiliary supporting base 63, it is possible to have a structure of attaching the free bearings 65 only to the second auxiliary supporting base 63 and providing a suction groove on the first auxiliary supporting base 62, as provided in the center table 61.

Further, it is possible to provide a groove section on each surface of the first auxiliary supporting base 62 and the second auxiliary supporting base 63 where the substrate 33 is mounted, as provided in the center table 61. In this case, in addition to the fact that the center table 61 vacuum-suctions and holds the central portion of the substrate 33 using vacuum means (e.g., a vacuum pump, a suction motor or the like), an outer circumferential portion of the substrate 33 slightly away from the center of the substrate 33 is vacuum-suctioned and held by using vacuum means (e.g., a vacuum pump, a suction motor or the like). Thus, the substrate 33 is held extremely firmly. In this case, when the entire table unit 60 is rotated, the large-sized substrate 33 generates a large rotating moment. However, the substrate 33 is fixedly held by the first auxiliary supporting base 62 and the second auxiliary supporting base 63. Hence, there is no concern of the substrate 33 rotating and moving, thus assuringly preventing the displacement of the substrate 33.

It is possible to provide in the polishing unit 40 a a substrate side edge portion holding means for fixing a side edge portion of the substrate 33, supported by the substrate side edge portion supporting means 42, from the upper side of the substrate 33. FIG. 13 is a side view showing the polishing unit 40 a when the substrate side edge portion holding means is provided. FIG. 14 is a front view of the polishing unit 40 a when the substrate side edge portion holding means is provided.

As shown in FIG. 13 and FIG. 14, a plurality of free bearings 50H is provided on the lower surface of the horizontal base plate 52 in the polishing unit 40 a, as the substrate side edge portion holding means. Each free bearing 50H has a similar structure to the free bearing 50 provided on the supporting plate portion 42 a of the substrate side edge portion supporting means 42. Similar to the free bearings 50 provided on the substrate side edge portion supporting means 42, the free bearings 50H are arranged on the lower surface of the horizontal base plate 52 and around the opening portion 52 a provided in the central portion of the horizontal base plate 52 such that the large balls 50 a are positioned at the lower side of the respective free bearings 50H.

Different from the case of the polishing unit 40 a as shown in FIG. 2 and FIG. 3, the horizontal base plate 52 is attached to the lower end portion of an upward-and-downward plate 57, which is arranged in a horizontal state along the vertical base plate 51.

The upward-and-downward plate 57 is movable in the up-down direction (Z-axis direction) by a plate upward-and-downward mechanism (not shown). The plate upward-and-downward mechanism is structured to move the upward-and-downward plate 57 upward and downward by LM guides, a ball screw and a servo motor, which are provided on the polishing unit holding body 83A along the Z-axis. The plate upward-and-downward mechanism is not limited to such a structure. The plate upward-and-downward mechanism may be structured by a linear motor, a cylinder or the like.

The horizontal base plate 52 is positioned to a predetermined height by the plate upward-and-downward mechanism. The supporting base plate portion 42 a of the substrate side edge portion supporting means 42 is positioned, by the cylinder 53 provided on the horizontal base plate 52, at a level lower than the horizontal base plate 52 by a predetermined height.

At the time of polishing the substrate 33, the free bearings 50H suppress the upward movement of the end face 33 a of the substrate 33 by holding the vicinity of the end face 33 a of the substrate 33 from the upper side of the substrate 33. When the polishing unit 40 a is moved along the end face 33 a of the substrate 33, the free bearings 50H slide while contacting the upper surface of the substrate 33. However, since the friction with respect to the upper surface of the substrate 33 is small, the free bearings 50H moves smoothly on the upper surface of the substrate 33.

The rest of the structure is the same as that of the polishing unit 40 a shown in FIG. 2 and FIG. 3. Thus, the same structural elements are denoted by the same reference numbers, and the description thereof will be omitted.

The operation of the polishing unit 40 a having such a structure will be described. First, the horizontal base plate 52 is moved up to a waiting position by plate the upward-and-downward mechanism. The supporting plate portion 42 a of the substrate side edge portion supporting means 42 is moved down to a waiting position by the cylinder 53 provided on the horizontal base plate 52. In this state, the polishing unit holding moving mechanism 81A is moved in the Y-axis direction to move closer to the center table 61 where the central portion of the substrate 33 is mounted, and an side edge portion of the substrate 33 is positioned between the supporting plate portion 42 a of the substrate side edge portion supporting means 42 and the horizontal base plate 52 of the polishing head 41, as shown in FIG. 15.

In this state, the horizontal base plate 52 is lowered, and the crest of the lower end of each of the free bearings provided on the lower surface of the horizontal base plate 52 is moved to the position (Z0+ΔZ′), which is higher than the height (Z0) of the upper surface of the center table 61 by the thickness (ΔZ′) of the substrate 33 mounted and fixed on the center table 61. Thereafter, the supporting plate portion 42 a is moved upward by the cylinder 53 provided on the horizontal base plate 52, and the crest of the upper end of each of the free bearings 50 provided on the supporting plate portion 42 a is moved to the same height (Z0) as the upper surface (Z0) of the center table 61.

As a result, as shown in FIG. 16, the lower surface of the side edge portion of the substrate 33 mounted on the center table 61 is supported by the free bearings 50 provided on the supporting plate portion 42 a and at the same time, held by the free bearings 50H provided on the horizontal base plate 52. Thereafter, the end face 33 a of the substrate 33 is polished by a similar operation to the operation described above.

The polishing work of the end surface 33 a of the substrate 33 is performed by the polishing grind stone 45 i of the polishing grind stone set 45, the central portion of the polishing grind stone 45 i in the up-down direction is denoted as polishing position P3. The polishing position P3 is a position which is higher than the height of substrate 33 by ½ of the thickness of the substrate 33 (Z0+ΔZ′/2) with respect to height Z0 of the center of the center table 61. This processing position varies depending on the shape of the polishing grind stone 45 i and the like.

As described above, the polishing is performed while the lower surface and the upper surface of the side edge portion in the vicinity of the end face 33 a of the substrate 33 are held by the free bearings 50 and the free bearings 50H. Thus, bending, undulations and the like of the side edge portion of the substrate 33 are suppressed. Therefore, the end face 33 a of the substrate 33 can be stably polished at a high precision. Sliding friction of each of the free bearing 50 and the free bearing 50H with respect to the substrate 33 is small. Thus, there is no concern of causing any damages to the upper surface and the lower surface of the substrate 33. Instead of the free bearings 50H provided on the horizontal base plate 52, it is possible to use a pad made of a material with low sliding friction (e.g., fluoresin (registered trademark “Teflon”)).

In the case of the large-sized substrate 33, the auxiliary substrate supporting mechanism 67 is used as described above.

Next, a first method of chamfering four end faces of a piece of the substrate 33 in order using the polishing apparatus 80A according to the present invention will be described with reference to FIG. 17. FIG. 17 only shows the polishing unit 40 a, the image capturing device 49A, the polishing unit holding body 83A and the substrate 33. FIG. 17 also describes a positional relationship between the substrate 33 and the polishing unit 40 a or a positional relationship between the substrate 33 and the image capturing device 49A.

The substrate 33 is a bonded substrate for which the lower substrate b and the upper substrate c are bonded to each other. The lower substrate b is slightly larger than the upper substrate c, and a short-circuit electrode for protecting a circuit is formed on an outer circumferential portion of the lower substrate b. The polishing unit 40 a moves along the end face 33 a of the substrate 33 at the time of processing.

First, the substrate (bonded substrate) 33 which has been cut from a mother substrate is mounted on the center table 61 of the table unit 60. In this case, the substrate 33 having the shape of rectangular is mounted on the center table 61 such that the longer side of the substrate 33 is the X-axis direction and the width direction is the Y-axis direction. As shown in Portion (1) of FIG. 17, a corner portion located in the −X-axis direction of X-Y coordinate axis at an end face of the substrate 33 mounted on the center table 61 adjacent to the polishing unit holding body 83A is denoted as A, a corner portion located in the +X-axis direction with respect to the corner portion A is denoted as B, a corner portion located in the +Y-axis direction with respect to the corner portion B is denoted as C, and a corner portion located in the −X-axis direction with respect to the corner portion C is denoted as D.

When the substrate 33 is positioned with respect to the center table 61 of the table unit 60 with guide pins or the like and fixedly held on the center table 61, the image capturing device 49A captures the pair of the alignment marks provided on the substrate 33. In this case, the image capturing device 49A first captures the position of one of the alignment marks located in the vicinity of the corner portion B as shown in Portion (1) of FIG. 17 and then captures the position of the other alignment mark located in the vicinity of the corner portion A as shown in Portion (2) of FIG. 17. After the completion of the capture by the image capturing device 49A, the control section 88, based on the positional data of the two alignment marks, computes a tilted angle in a horizontal direction with respect to a normal state of substrate 33 and stores the result thereof in a memory of the control section 88.

In the substrate 33 cut from a mother substrate, a cutting line and a straight line connecting the alignment marks are often not completely parallel to each other. Therefore, when the polishing unit 40 a is moved in the X-axis direction during polishing based on the positional data of the substrate 33 based on the pair of the alignment marks stored in the memory of the control section 88, the polishing unit 40 a is also moved in Y axis-direction, so that the end face 33 a of the substrate 33 is polished in parallel to the straight line connecting the pair of alignment marks.

Next, the polishing grind stone set 45 of the polishing unit 40 a located in the vicinity of a corner portion of the substrate 33 is rotated, and the polishing grind stone 45 i of the polishing grind stone set 45 is positioned to polish the corner portion A. When the polishing unit 40 a is moved from the corner portion A to the corner portion B of the substrate 33, an end face between the corner portion A and the corner portion B is chamfered. In the case, the control section 88 performs a linear interpolation by moving the polishing unit holding body 83A in the Y-axis direction based on the data stored in the memory along with the movement of the polishing unit 40 a in the X-axis direction.

Thereafter, as shown in Portion (3) of FIG. 17, when the polishing work of the end face from the corner portion A to the corner portion B of the substrate 33 is completed, the entire polishing unit holding body 83A is moved in the −Y-axis direction to move away from the center table 61 and the polishing unit 40 a is moved in the −X-axis direction along the polishing unit holding body 83A. Accordingly, the polishing unit 40 a is moved to a point of waiting position H. The point H is set such that the polishing unit 40 a does not hit the rectangular substrate 33 even when the substrate 33 is rotated with the center table 61 as its center.

Next, as shown in Portion (4) of FIG. 17, the entire table unit 60 is operated to rotate the substrate 33 by 90 degrees such that the corner portion D of the substrate 33 is adjacent to the waiting position H of the polishing unit 40 a. Then, the polishing unit 40 a is positioned by the movement of the polishing unit holding body 83A and the polishing unit 40 a such that the corner portion D of the substrate 33 is polished. As shown in Portion (5) of FIG. 17, the polishing unit 40 a is moved in the +X-axis direction along the polishing unit holding body 83A so as to polish an end face located between the corner portion D and the corner portion A, from the corner portion D toward the corner portion A.

When the polishing work of the end face from the corner portion D to the corner portion A of the substrate 33 is completed, as shown in Portion (6) of FIG. 17, the entire polishing unit holding body 83A is moved in the −Y-axis direction to move away from the center table 61 and the polishing unit 40 a is moved in the −X-axis direction along the polishing unit holding body 83A. Accordingly, the polishing unit 40 a is moved to a point of waiting position H.

Next, the entire table unit 60 is operated to rotate the substrate 33 by 90 degrees such that the corner portion C of the substrate 33 is adjacent to the waiting position H of the polishing unit 40 a. Then, the polishing unit 40 a is positioned by the movement of the polishing unit holding body 83A and the polishing unit 40 a such that the corner portion C of the substrate 33 is polished. As shown in Portion (7) of FIG. 17, the polishing unit 40 a is moved in the +X-axis direction along the polishing unit holding body 83A so as to polish an end face located between the corner portion C and the corner portion D, from the corner portion C toward the corner portion D.

When the polishing work of the end face from the corner portion C to the corner portion D of the substrate 33 is completed, as shown in Portion (8) of FIG. 17, the entire polishing unit holding body 83A is moved in the −Y-axis direction to move away from the center table 61 and the polishing unit 40 a is moved in the −X-axis direction along the polishing unit holding body 83A. Accordingly, the polishing unit 40 a is moved to a point of waiting position H.

Next, the entire table unit 60 is operated to rotate the substrate 33 by 90 degrees such that the corner portion B of the substrate 33 is adjacent to the waiting position H of the polishing unit 40 a. Then, the polishing unit 40 a is positioned by the movement of the polishing unit holding body 83A and the polishing unit 40 a such that the corner portion B of the substrate 33 is polished. As shown in Portion (9) of FIG. 17, the polishing unit 40 a is moved in the +X-axis direction along the polishing unit holding body 83A so as to polish an end face located between the corner portion B and the corner portion C, from the corner portion B toward the corner portion C.

As described above, the four end faces of the substrate 33 held on the table unit 60 are chamfered by rotating the substrate 33 three times by 90 degrees each time.

FIG. 18 is an explanatory diagram for a second method for chamfering the four end faces of the substrate 33 using the polishing apparatus 80A according to the present invention. Similar to the case shown in FIG. 17 the image capturing device 49A first captures the position of one of the alignment marks located in the vicinity of the corner portion B as shown in Portion (1) of FIG. 18 and then captures the position of the other alignment mark located in the vicinity of the corner portion A as shown in Portion (2) of FIG. 18. After the completion of the capture by the image capturing device 49A, the control section 88, based on the positional data of the two alignment marks, computes a tilted angle of the substrate 33 in a horizontal direction and stores the result thereof in a memory of the control section 88.

Thereafter, chamfering starts from the point where capturing by the image capturing device 49A was complete (i.e., the corner portion A). As shown in Portion (3) of FIG. 18, the polishing unit 40 a is moved toward the corner portion B. In this case, the control section 88 moves the polishing unit holding body 83A in the Y-axis direction based on the data stored in the memory along with the movement of the polishing unit 40 a in the X-axis direction.

Next, as shown in Portion (4) of FIG. 18, the polishing unit holding body 83A is moved in the Y-axis direction without rotating the substrate 33 by the table unit 60, so that the polishing unit 40 a chamfers an end face located between the corner portion B and the corner portion C, from the corner portion B toward the corner portion C. Similarly, in this case, the control section 88 moves the polishing unit 40 a in the X-axis direction based on the data stored in the memory along with the movement of the polishing unit holding body 83A in the Y-axis direction.

Next, the entire polishing unit holding body 83A is moved in the −Y-axis direction to move away from the center table 61 and the polishing unit 40 a is moved in the −X-axis direction along the polishing unit holding body 83A. Accordingly, the polishing unit 40 a is moved to a point of waiting position H, as shown in Portion (5) of FIG. 18.

Next, the entire table unit 60 is operated to rotate the substrate 33 by 90 degrees such that the corner portion D of the substrate 33 is adjacent to the waiting position H of the polishing unit 40 a. Then, the polishing unit holding body 83A is moved in the Y-axis direction to move closer to the center table 61 and the polishing unit 40 a is moved along the X-axis direction along the polishing unit holding body 83A such that the corner portion A of the substrate 33 is polished. As shown in Portion (6) of FIG. 18, the polishing unit 40 a is moved in the −X-axis direction along the polishing unit holding body 83A so as to polish an end face located between the corner portion A and the corner portion D, from the corner portion A toward the corner portion D.

Thereafter, as shown in Portion (7) of FIG. 18, the polishing unit holding body 83A is moved in the Y-axis direction without rotating the substrate 33 by the table unit 60, so that the polishing unit 40 a chamfers an end face located between the corner portion B and the corner portion C, from the corner portion B toward the corner portion C. Similarly, in this case, the control section 88 moves the polishing unit 40 a in the X-axis direction based on the data stored in the memory along with the movement of the polishing unit holding body 83A in the Y-axis direction.

In this case, the substrate 33 is only rotated by 90 degrees by the table unit 60 twice instead of three times, thereby improving the working efficiency of chamfering.

FIG. 19 is an explanatory diagram for a third method for chamfering the four end faces of the substrate 33 using the polishing apparatus 80A according to the present invention. Similar to the case shown in FIG. 18, the image capturing device 49A first captures the position of one of the alignment marks located in the vicinity of the corner portion B as shown in Portion (1) of FIG. 19 and then captures the position of the other alignment mark located in the vicinity of the corner portion A as shown in Portion (2) of FIG. 19. After the completion of the capture by the image capturing device 49A, the control section 88, based on the positional data of the two alignment marks, computes a tilted angle of the substrate 33 in a horizontal direction and stores the result thereof in a memory of the control section 88.

Thereafter, chamfering starts from the point where the capturing by the image capturing device 49A was completed (i.e., the corner portion A). As shown in Portion (3) of FIG. 19, the polishing unit 40 a is moved toward the corner portion B. In this case, the control section 88 moves the polishing unit holding body 83A in the Y-axis direction based on the data stored in the memory along with the movement of the polishing unit 40 a in the X-axis direction.

Next, as shown in Portion (4) of FIG. 19, the polishing unit holding body 83A is moved in the Y-axis direction without rotating the substrate 33 by the table unit 60, so that the polishing unit 40 a chamfers an end face located between the corner portion B and the corner portion C, from the corner portion B toward the corner portion C. Similarly, in this case, the control section 88 moves the polishing unit 40 a in the X-axis direction based on the data stored in the memory along with the movement of the polishing unit holding body 83A in the Y-axis direction.

Next, the entire polishing unit holding body 83A is moved in the −Y-axis direction to move away from the center table 61 and the polishing unit 40 a is moved in the −X-axis direction along the polishing unit holding body 83A. Accordingly, the polishing unit 40 a is moved to a point of waiting position H, as shown in Portion (5) of FIG. 19.

The steps of the third method so far are similar to those of the second method shown in FIG. 18.

Next, the entire table unit 60 is operated to rotate the substrate 33 by 180 degrees such that the corner portion C of the substrate 33 is adjacent to the waiting position H of the polishing unit 40 a. Then, the polishing unit holding body 83A is moved in the Y-axis direction to move closer to the center table 61 and the polishing unit 40 a is moved along the X-axis direction along the polishing unit holding body 83A such that the corner portion C of the substrate 33 is polished. As shown in Portion (6) of FIG. 19, the polishing unit 40 a is moved in the −X-axis direction along the polishing unit holding body 83A so as to polish an end face located between the corner portion C and the corner portion D, from the corner portion C toward the corner portion D.

Thereafter, as shown in Portion (7) of FIG. 19, the polishing unit holding body 83A is moved in the Y-axis direction without rotating the substrate 33 by the table unit 60, so that the polishing unit 40 a chamfers an end face located between the corner portion D and the corner portion A, from the corner portion D toward the corner portion A. Similarly, in this case, the control section 88 moves the polishing unit 40 a in the X-axis direction based on the data stored in the memory along with the movement of the polishing unit holding body 83A in the Y-axis direction.

In the case of the third method, the substrate 33 is only rotated by 180 degrees by the table unit 60 once, thereby improving the working efficiency of chamfering.

According to the polishing apparatus of the present invention, the polishing unit 40 a is arranged in the X-axis direction to be positioned striding above the table unit 60, and the polishing unit 40 a is provided to be movable in the X-axis direction on the polishing unit holding body 83A, which is movable in the Y-axis direction. Therefore, without rotating the table unit 60, it is possible for the polishing unit 40 a to chamfer three end faces 33 a of the substrate 33 mounted on the table unit 60. Further, if the substrate 33 is rotated once by the table unit 60 by 90 degrees and 180 degrees, it is possible to chamfer the remaining end face of the substrate 33. The timing of rotating the substrate 33 by 90 degrees or 180 degrees is set appropriately in consideration of the working efficiency.

The substrate 33 can be rotated in either clockwise or anti-clockwise direction. In addition, when the polishing unit 40 a is moved along corner portions at the respective corner portions of the end faces 33 a of the substrate 33, it is possible to chamfer upper and lower edges of the corner portions. In this case, it is possible to perform both C-face chamfering and round chamfering of the corner portions.

Embodiment 2

FIG. 20 is a perspective view schematically showing a structure of a polishing apparatus according to Embodiment 2 of the present invention. The polishing apparatus 80B according to Embodiment 2 has a similar structure to that of the polishing apparatus 80A according to Embodiment 1 except that a second polishing unit holding body 83B is provided in addition to the polishing unit holding body 83A (hereinafter, this polishing unit holding body 83A is referred to as the first polishing unit holding body 83A) in the polishing apparatus 80A according to Embodiment 1. The second polishing unit holding body 83B has a similar structure to that of the first polishing unit holding body 83A, and a second polishing unit 40 b, an image capturing device 49B and the like are provided on the second polishing unit holding body 83B. The second polishing unit holding body 83B is movable by a second guide body moving mechanism 81B, along a pair of LM guides 84 provided on the upper surface of the base mount 82. The guide body moving mechanism 81B is provided on the LM guides 84, which are different from the LM guides 84 where the guide body moving mechanism 81A is provided in order to drive the first polishing unit holding body 83A.

The second guide body moving mechanism 81B, a polishing unit moving mechanism 85B for moving the second polishing unit 40 b in the X-axis direction and the like are controlled by the control section 88. The rest of the structure of the polishing apparatus 80B according to Embodiment 2 is similar to that of the polishing apparatus 80A according to Embodiment 1.

The polishing apparatus 80B according to Embodiment 2 having such a structure includes the polishing unit 40 a and the second polishing unit 40 b. Accordingly, even in a state in which the substrate 33 is fixed by the table unit 60, it is possible to simultaneously chamfer two end faces of the substrate 33 facing each other.

FIG. 21 is an explanatory diagram for a method for chamfering the four end faces of the substrate 33 using the polishing apparatus 80B according to Embodiment 2. First, as shown in Portion (1) of FIG. 21, the table unit 60 is set at a predetermined reference position, and the substrate 33 is mounted on the table unit 60 to be fixedly held thereon. In this case, the substrate 33 is held such that the shorter side of the substrate 33 is parallel to Y-axis or the longer side of the substrate 33 is parallel to X-axis. In FIG. 21, corners of the substrate 33 are denoted as A, B, C and D, respectively, as in the case of the explanatory diagram shown in FIG. 17.

Next, the first polishing unit holding body 83A is moved to be positioned in the vicinity of an end face between the corner portion A and the corner portion B of the substrate 33 such that the image capturing device 49A can capture an alignment mark at the corner portion A. Also, the second polishing unit holding body 83B is moved to be positioned in the vicinity of an end face between the corner portion A and the corner portion B of the substrate 33 such that the image capturing device 49B can capture an alignment mark at the corner portion B. In such a state, the alignment mark at the corner portion A is captured by the image capturing device 49A and the alignment mark at the corner portion B is captured by the image capturing device 49B.

Next, the image processing device 89 generates position coordinate data of the two alignment marks from the image data of the alignment marks captured by the image capturing devices 49A and 49B, respectively. The control section 88 computes the tilt of the substrate 33 with respect to the X-axis direction using the position coordinate data sent from the image processing device 89, accurately recognizes the state of the substrate 33 on the table unit 60 and stores positional data in a memory of the control section 88.

Next, the first polishing unit holding body 83A and the polishing unit 40 a are moved such that the polishing unit 40 a of the first polishing unit holding body 83A is positioned at a waiting position, which is similar to the waiting position H shown in Portion (4) of FIG. 17, and the second unit holding body 83B and the polishing unit 40 b are moved such that the polishing unit 40 b of the second polishing unit holding body 83B is positioned at a waiting position, which is point-symmetrical with respect to the waiting position H with having the center of the center table 61 as their center.

Thereafter, as shown in Portion (2) of FIG. 21, the table unit 60 is rotated clockwise by the control section 88 by a predetermined degree φ, thereby the substrate 33 being rotated in a similar manner. The degree φ depends on the ratio of the longer side and the shorter side of the substrate 33; however, it is preferably one of 30 degrees, 45 degrees and 60 degrees.

Next, the polishing unit 40 a of the first polishing unit holding body 83A is positioned to polish the corner portion D, and the polishing unit 40 b is positioned to polish the corner portion B. In this case, as shown in Portion (2) of FIG. 21, the corner portion A of the substrate 33 is positioned below the first polishing unit holding body 83A. However, there is no concern that the polishing unit 40 a and the substrate 33 would interfere with each other since the polishing unit 40 a is moved along the Y-axis direction from the waiting position H. Also, the corner portion C of the substrate 33 is positioned below the second polishing unit holding body 83B. However, there is no concern that the polishing unit 40 b and the corner portion C of the substrate 33 would interfere with each other since the polishing unit 40 b is moved along the Y-axis direction from a waiting position, which is distant from the corner portion C of the substrate 33 in the Y-axis direction and the X-axis direction.

In such a situation, the first polishing unit holding body 83A is moved in the −Y-axis direction such that the polishing unit 40 a of the first polishing unit holding body 83A polishes an end face between the corner portion D and the corner portion A, from the corner portion D toward the corner portion A, and the polishing unit 40 a is moved in the X-axis direction. Concurrently, the second polishing unit holding body 83B is moved in the Y-axis direction such that the polishing unit 40 b of the second polishing unit holding body 83B polishes an end face between the corner portion B and the corner portion C, from the corner portion B toward the corner portion C, and the polishing unit 40 b is moved in the −X-axis direction.

In this case, a rotation angle of the substrate 33 in a horizontal direction based on the positional data of the corner portions A and B of the substrate 33 of an initial state is stored in the memory of the control section 88, and a rotation angle φ of the table unit 60 is also stored in the control section 88. Accordingly, the control section 88 computes the travel data of the polishing units 40 a and 40 b using the positional data and stores the travel data in the memory of the control section 88. Thus, the control section 88 controls the movement of the first polishing unit holding body 83A and the polishing unit 40 a based on the travel data of the polishing units 40 a and 40 b stored in the memory to move the first polishing unit holding body 83A and the polishing unit 40 a along the end face between the corner portion D and the corner portion A and the control section 88 also controls the movement of the second polishing unit holding body 83B, and the polishing unit 40 b to move the second polishing unit holding body 83B and the polishing unit 40 b along the end face between the corner portion B and the corner portion C.

When the polishing unit 40 a of the first polishing unit holding body 83A reaches the corner portion A, the first polishing holding body 83A and the polishing unit 40 a are controlled such that the polishing unit 40 a is moved along the corner portion A. As a result, each of the end faces of the corner portion A is polished. Similarly, when the polishing unit 40 b of the second polishing unit holding body 83B reaches the corner portion C, the second polishing holding body 83B and the polishing unit 40 b are controlled such that the polishing unit 40 b is moved along the corner portion C. As a result, each of the end faces of the corner portion C is polished.

Thereafter, as shown in Portion (4) of FIG. 21, the first polishing unit holding body 83A is moved in the Y-axis direction such that the polishing unit 40 a of the first polishing unit holding body 83A polishes an end face between the corner portion A and the corner portion B, from the corner portion A toward the corner portion B, and the polishing unit 40 a is moved in the X-axis direction. Concurrently, the second polishing unit holding body 83B is moved in the Y-axis direction such that the polishing unit 40 b of the second polishing unit holding body 83B polishes an end face between the corner portion C and the corner portion D, from the corner portion C toward the corner portion D, and the polishing unit 40 b is moved in the −X-axis direction.

Thereafter, the polishing unit 40 a of the first polishing unit holding body 83A reaches the corner portion B and the polishing unit 40 b of the second polishing unit holding body 83B reaches the corner portion D, and hence chamfering of the four end faces of the substrate 33 is completed.

As described above, in the steps shown in Portion (2) to Portion (4) of FIG. 21, it is possible to chamfer the four end faces of the substrate 33 and at same time chamfer all the corner portions of the substrate 33. In addition, after completion of the steps up to the one shown in Portion (4) of FIG. 21, as shown in Portion (5) of FIG. 21, the table unit 60 is rotated such that the longer side of the substrate 33 is along the X-axis direction and thereafter, the corner portion B is chamfered by the polishing unit 40 a of the first polishing unit holding body 83A, and the corner portion D is chamfered by the polishing unit 40 b of the second polishing unit holding body 83B. Still thereafter, the corner portion A is chamfered by the polishing unit 40 a of the first polishing unit holding body 83A, and the corner portion C is chamfered by the polishing unit 40 b of the second polishing unit holding body 83B.

As described above, according to the polishing apparatus 80B of the present invention, the table unit 60 is rotated by predetermined angles (30 degrees, 45 degrees, 60 degrees) in the XY plane with the center of the center table 61 as its axis, and the two polishing units 40 a and 40 b are moved to be positioned at the respective corner portions on the diagonal lines of the substrate 33. Thereafter, consecutive end faces of the substrate 33 are polished in a continuous manner by the polishing unit 40 a and the polishing unit 40 b without rotating the substrate 33, thereby significantly improving the working efficiency of chamfering the end faces of the substrate 33.

Further, the work of chamfering all the end faces of the substrate 33 can be performed without causing interference between the first polishing unit holding body 83A and the second polishing unit holding body 83B. With the change of the moving direction of the polishing unit 40 a and the polishing unit 40 b at the corners of the substrate 33, it is possible to chamfer end faces at the corners of the substrate 33 and it is also possible to easily change the chamfering at a corner portion to C-face chamfering or round chamfering.

Embodiment 3

FIG. 22 is a plan view schematically showing a structure of a polishing apparatus according to Embodiment 3 of the present invention. This polishing apparatus 90 includes: four polishing units 91, four moving guide bodies 92; four polishing unit moving mechanisms 99; a center table 100; an image processing device 101; a control section 102; and four polishing unit feeding mechanisms (not shown).

The polishing apparatus 90 according to the present embodiment includes: a rectangular center table 100 for mounting the central portion of the substrate 33 and suction-holding the substrate 33; four moving guide bodies 92 arranged along respective side edges of the center table 100; four polishing units 91 provided to be movable along the respective moving guide bodies 92; polishing unit moving mechanisms 99 for moving the polishing units 91 in both directions along the respective moving guide bodies 92; and a polishing unit feeding mechanism (not shown) for moving the respective polishing units 91 in both directions along the direction given by arrow P in FIG. 22, wherein the direction of given by arrow P is a direction perpendicular to the respective moving guide body 92 in the XY plane (direction perpendicular to end faces of the center table).

In addition, air blowing devices 96 are provided on the respective polishing units 91 of the polishing apparatus 90. Further, the polishing apparatus 90 includes: an image processing device 101 for processing images captured by each of the image capturing devices 49; and a control section 102 for computing the positional data of the alignment marks provided on the substrate 33 based on output data from the image processing device 101 and for controlling the operation of the polishing apparatus 90. The polishing unit moving mechanism 99 is given a control signal from the control section 102 for driving. In FIG. 22, only one image processing device 101 is shown; however, two or more image processing devices 101 may be provided. The image processing device 101 processes image data captured by the image processing devices 49 in order. Therefore, one image processing device 101 can process images sent from a plurality of image capturing devices 49.

Each of the polishing units 91 has a similar structure to that of the polishing unit 40 a according to Embodiment 1 and includes: a polishing grind stone set 45 capable of moving in the Z-axis direction; and a polishing head moving mechanism for moving the polishing grind stone set 45 in the Z-axis direction. Each of image capturing devices 49 is provided on an opposite side with respect to the moving direction of the polishing grind stone set 45 at the time of chamfering by the polishing grind stone set 45. In addition, each air blowing device 96 is provided between the polishing grind stone set and the image capturing device in order to blow away polishing powder generated by the polishing grind stone set 45, working liquid and the like. It is possible by a micrometer head to adjust the height of the image capturing device 49 and the air blowing device 96 from the substrate 33 and it is also possible to adjust the position of the image capturing device 49 and the air blowing device 96 with respect to an end face of the substrate. The air blowing device 96 is connected to an air pump (not shown) to blow compressed air to the image capturing device 49.

Based on the positional data of the alignment marks processed by the image processing device 101, the control section 102 computes the tilt of the substrate 33 mounted on the center table 100 with respect to the X-axis direction; computes a feeding amount (entering amount) of a polishing grind stone of the polishing grind stone set of each of the polishing units 91 with respect to the substrate 33; and also controls the polishing unit moving mechanisms 99 and the polishing unit feeding mechanisms (not shown) for moving the polishing grind stones along the respective end faces of the tilted substrate 33. In addition, the control section 102 includes a function for comparing a predetermined set value and an actual polished amount to control each of the polishing unit feeding mechanisms so as to make the amount of chamfering of the substrate constant to each other.

The center table 100 has a suction surface thereon in parallel with the XY plane. However, a mechanism for rotating the table is not provided with the center table 100. At the bottom surface of the center table 100, a sound sensor is provided in order to sense that the polishing unit 91 has contacted the end face of the substrate 33. This sound sensor detects vibrations generated at the center table 100 through the substrate 33 so as to sense the contact of the polishing unit 91 with the substrate 33.

The polishing unit moving mechanisms 99 are structured by the moving guide bodies 92 respectively provided along the side edges of the center table 100 (i.e., the end faces 33 a of the substrate 33 mounted and held on the center table 100), a ball screw (not shown) and a servo motor (not shown), and the polishing unit moving mechanisms 99 move the polishing unit 91 in both directions from a first position to a second position along the moving guide bodies 92 provided along the respective end faces of the center table 100 (the respective end faces 33 a of the substrate 33. The structure of the polishing unit moving mechanism 99 is not limited with the ball screw and the servo motor. It may also be structured by a linear motor.

The polishing unit feeding mechanism is structured by LM guides (not shown), a ball screw (not shown) and a servo motor (not shown). Each of the polishing unit feeding mechanisms has a function of moving the respective polishing unit 91 the direction given by arrow P in the figure (i.e., in a direction of moving the polishing unit 91 closer to and away from the respective end face 33 a of the substrate 33) and gradually feeding the polishing grind stone of the respective polishing unit 91 to the respective end face 33 a of the substrate 33. Structural elements of the polishing unit feeding mechanism are not limited to the LM guides, the ball screw and the servo motor. They may also be the LM guides and a linear motor.

Next, a procedure of simultaneously processing the four end faces 33 a of the substrate 33 will be described. First, the center table 100 mounts and suction-holds the substrate 33. Next, the image capturing devices 49 capture the alignment marks provided on the substrate 33, so that the captured image data is processed by the image processing device 101, and as a result, the positional data of the alignment marks is generated. The control section 102 computes a displacement amount of the substrate 33 in the X-axis direction and the Y-axis direction with respect to a reference position from the positional data of the alignment marks which have been output from the image processing device 101. Based on the computed result, the control section 102 computes the tilt of the substrate 33 with respect to the X-axis direction and the Y-axis direction and a polishing start position and a polishing end position of each of the polishing units 91 for the substrate 33.

Then, the control section 102 controls the moving direction of each of the polishing unit moving mechanisms 99 and each of the polishing unit feeding mechanisms in the X-axis direction and the Y-axis direction (direction given by arrow R and direction given by arrow P); the polishing start direction; and the polishing end direction (hereinafter, this control is referred to as a linear interpolation). Accordingly, even if the substrate 33 is not held on the center table 100 at a predetermined posture (i.e., even if the substrate 33 is tilted in a horizontal direction with respect to the reference position), it is possible to polish the end faces 33 a of the substrate 33.

Thereafter, the polishing units 91 move the respective polishing grind stones along the direction given by arrow P to move closer to the respective end faces 33 a of the substrate 33 while rotating the polishing grind stones. With the sound sensor provided on the bottom surface of the table unit 100, vibrations generated at the table unit 100 are sensed so as to detect that the polishing units 91 have contacted the respective end faces 33 a of the substrate 33. Thus, the control unit 88 detects the point 0 of an initial position where the polishing units 91 contact the respective end faces 33 a of the substrate 33, on which polishing has not been performed yet. Thereafter, rotation of the polishing grind stones of the respective polishing units 91 is stopped and the polishing units 91 are moved to the respective waiting positions.

Next, the polishing grind stone of each of the polishing units 91 is rotated. In this state, the polishing units 91 are moved in the direction given by arrow R shown in FIG. 22, by the respective polishing unit moving mechanisms 99 while side edge portions of the substrate 33 are supported by respective substrate side edge portion supporting means and while the end faces 33 a of the substrate 33 are polished by the respective polishing grind stones 45. In this case, based on the computed tilt of the substrate 33 with respect to X direction and Y direction and the polishing start position and the polishing end position of the substrate 33, the control section 102 moves the polishing units 91 in the R direction by the respective polishing unit moving mechanisms 99 and concurrently moves the polishing units 91 in the P direction by the respective polishing unit feeding mechanisms 99. As a result, the polishing units 91 correct the displacement amount of the substrate 33 due to the linear interpolation and at the same time polish the respective end faces 33 a of the substrate 33 in a continuous manner.

The polishing unit 90 according to the present embodiment can simultaneously process the four end faces 33 a of the substrate 33 by the four polishing units 91 as described above. In addition, the polishing units 91 of the polishing apparatus 90 are moved along respective corner portions of the substrate 33 at the time of start of polishing or at the end of polishing when the polishing units 91 are located at the respective corner portions of the substrate 33, so that all the corner portions of the substrate 33 can be chamfered at once. Further, by controlling the moving direction when the polishing units 91 are moved along the respective corner portions of the substrate 33, it is possible to perform chamfering of the corner portions of the substrate 33 by either C-face chamfering or round chamfering.

In addition, when the polishing units 91 are simultaneously moved by the respective polishing unit moving mechanisms 99 in the R direction and at the same time the substrate is chamfered, the air blowing devices 96 arranged behind the moving direction of the respective polishing grind stones 45 blow highly compressed air. This highly compressed air removes working liquid from the end faces 33 a of the substrate 33, which have been just chamfered by the respective polishing grind stones 45. The image capturing devices 49 arranged behind the respective polishing grind units 45 capture the respective end faces 33 a of the substrate 33, which have been chamfered by the respective polishing grind stones 45. The images obtained by the image capturing devices 49 are processed by image processing device 101 so as to detect the actual amount of chamfering of the polished substrate 33. The control section 102 compares the actual chamfered amount with preset chamfering amount of the upper limit value and the lower limit value to determine whether or not the actual chamfered amount of the substrate 33 deviate from the upper limit value and the lower limit value. When the actual chamfered amount deviate from one of the upper limit value and the lower limit value, the control section 102 controls the polishing unit moving mechanisms 99 and the polishing unit feeding mechanisms of the respective polishing units 91 to control the position of the polishing grind stones with respect to the respective end faces of the substrate 33 so as to correct the amount of the substrate 33 to be chamfered.

As described above, the air blowing devices remove the working liquid from the respective end faces of the substrate 33, which have been just chamfered by the respective polishing grind stones 45, and the image capturing devices 49 capture the respective end faces of the substrate 33, which have been just chamfered. As such, the control section 102 detects the chamfered amount and compares them with respective preset values to adjust the feeding amounts of the respective polishing grind stones 45 so to correct the amount to be chamfered. Owing to such a correction, it is possible to prevent the change of the amount to be chamfered due to an inclination of the substrate 33 with respect to a reference state, thereby always performing constant amount of chamfering. Therefore, the polishing can be performed at extremely high precision. If the amount of chamfering is reduced with respect to the feeding amount of the respective polishing grind stones 45, the control section 102 determines that polishing sections of the respective grind stones 45 are worn out. When the currently used grind stone 45 is part of a polishing grind stone set having a multiple layered structure, it is possible, by moving the polishing head by a predetermined amount in the up-down direction, such that polishing can be performed by a new polishing grind stone. Therefore, it is unnecessary to conduct any change of tools of the polishing grind stone, thus significantly improving the working efficiency.

The present embodiment employs a structure of holding the substrate 33 by the center table 100; however, instead of the center table 100, it is possible to use the rotatable table unit which is used in Embodiment 1. In this case, it is possible to have a structure of either rotating the center table or rotating the entire table unit by the table rotating mechanism. When the table unit rendered rotatable by the table rotating mechanism is used, the image capturing devices 49 capture the alignment marks provided on the substrate 33 mounted on the table unit, and the image processing device 101 recognizes the displacement of the substrate 33 from the image data of the respective image capturing devices 49, and the control section 102 rotates the table unit mounted on the substrate 33 by a predetermined amount of angles using the table rotating mechanism in order to correct the displacement amount. Then, chamfering work of the substrate 33 is performed with a state in which the correction has been made such that the moving direction of each of the polishing units 91 of the polishing apparatus 90 and the respective end face of the substrate are parallel to each other.

When the polishing apparatus 90 according to the present invention is used, the size of the center table 100 can be small, and there is no need for conducting any change of tools (e.g., change of tables for mounting the substrate) even when the size of the substrate varies. By supporting the end faces of the substrate to be polished, it is possible, without bending the substrate, to chamfer the end faces of the substrate at a high precision. In addition, since the four end faces of the substrate can be simultaneously chamfered, the chamfering can be performed with extremely high efficiency.

INDUSTRIAL APPLICABILITY

The polishing units and the polishing apparatuses according to the present invention can be used for a brittle substrate, such as semiconductor wafer, glass substrate, quartz substrate, ceramic substrate, and in particular, the polishing units and the polishing apparatuses according to the present invention can be used for apparatuses for manufacturing a large-sized flat panel display (FPD) including a liquid crystal display (LCD), a plasma display panel (PDP), an organic EL panel or transmissive liquid crystal projector substrate and reflective liquid crystal projector substrate, which are included in a liquid crystal projector, and a field emission display (FED), all of which are bonded substrates for which two single substrates are bonded to each other. 

1. A polishing apparatus comprising: a table unit, having a substrate mounted thereon, for fixedly holding the substrate in a predetermined reference state; a first polishing unit including a polishing grind stone for polishing an end face of the substrate held on the table unit and substrate side edge portion supporting means for supporting a lower surface of a side edge portion of the substrate in a vicinity of the end face of the substrate to be polished by the polishing grind stone; and a first polishing unit moving means for moving, together with the substrate side edge portion supporting means, the first polishing unit along the end face of the substrate while the polishing grind stone is polishing the end face of the substrate.
 2. A polishing apparatus according to claim 1, wherein the first polishing unit further includes substrate side edge portion holding means for holding an upper surface of the side edge portion of the substrate supported by the substrate side edge portion supporting means.
 3. A polishing apparatus according to claim 1, wherein the substrate side edge portion supporting means supports a lower surface of the substrate by a member having a low friction coefficient.
 4. A polishing apparatus according to claim 2, wherein the substrate side edge portion holding means holds an upper surface of the substrate by a member having a low friction coefficient.
 5. A polishing apparatus according to claim 3, wherein the material having the low friction coefficient is a free bearing.
 6. A polishing apparatus according to claim 4, wherein the material having the low friction coefficient is a free bearing.
 7. A polishing apparatus according to claim 1, wherein the table unit includes a center table, having a central portion of the lower surface of the substrate mounted thereon, for suctioning and holding the central portion.
 8. A polishing apparatus according to claim 7, wherein the table unit includes a plurality of substrate auxiliary supporting means, the plurality of substrate auxiliary supporting means being arranged around the center table to respectively support side portions of the lower surface of the substrate held on the center table.
 9. A polishing apparatus according to claim 8, wherein the substrate auxiliary supporting means includes an auxiliary supporting base for supporting the lower surface of the substrate, and the auxiliary supporting base is structured to support the lower surface of the substrate by a member having a low friction coefficient.
 10. A polishing apparatus according to claim 9, wherein the material having the low friction coefficient is a free bearing.
 11. A polishing apparatus according to claim 8, wherein the substrate auxiliary supporting means includes an auxiliary supporting base for supporting the lower surface of the substrate, and the auxiliary supporting base has means for suctioning and holding the lower surface of the substrate provided thereon.
 12. A polishing apparatus according to claim 9, wherein the substrate auxiliary supporting means includes a sliding mechanism for sliding the auxiliary supporting base closer to or away from the center table.
 13. A polishing apparatus according to claim 11, wherein the substrate auxiliary supporting means includes a sliding mechanism for sliding the auxiliary supporting base closer to or away from the center table.
 14. A polishing apparatus according to claim 8, wherein the table unit further includes a table rotating mechanism for rotating the center table.
 15. A polishing apparatus according to claim 14, wherein the table rotating mechanism rotates the substrate auxiliary supporting means together with the center table in an integrated manner.
 16. A polishing apparatus according to claim 14, wherein the first polishing unit and the first polishing unit moving means are attached to a first polishing unit holding body, the first polishing unit holding body having a first horizontal beam being arranged along the end face of the substrate held on the table unit, and the first polishing unit holding body is movable in a vertical direction with respect to the first horizontal beam.
 17. A polishing apparatus according to claim 16, wherein the first polishing unit is attached to be movable along the first horizontal beam of the first polishing unit holding body, and the first polishing unit moving means moves the first polishing unit along the first horizontal beam.
 18. A polishing apparatus according to claim 16, wherein an image capturing device is provided on the first polishing unit, the image capturing device being for capturing an image of an alignment mark provided on the substrate, the polishing apparatus further comprising: an image processing device for computing image data of the alignment mark captured by the image capturing device; and a control section for computing a rotation angle with respect to the reference state of the substrate mounted on the center unit based on positional data of the alignment mark computed by the image processing device.
 19. A polishing apparatus according to claim 17, further comprising: a second polishing unit including a polishing grind stone for polishing an end face, the end face being positioned on the opposite side of the end face to be polished by the first polishing unit for the substrate held on the table unit and substrate side edge portion supporting means for supporting the lower surface of the side edge portion of the substrate in the vicinity of the end face of the substrate to be polished by the polishing grind stone; and second polishing unit moving means for moving, together with the substrate side edge portion supporting means, the second polishing unit along the end face of the substrate while the polishing grind stone is polishing the end face of the substrate, wherein the second polishing unit and the second polishing unit moving means are attached to a second polishing unit holding body including a second horizontal beam in parallel with the first horizontal beam of the first polishing unit holding body, and the second polishing unit holding body is capable of being translated in a horizontal direction with respect to the second horizontal beam.
 20. A polishing apparatus according to claim 19, wherein the table rotating mechanism rotates the center table such that the substrate mounted on the center table is put in a state of being rotated by a predetermined angle of 30 to 60 degrees with respect to the reference state, and the first polishing unit and the second polishing unit simultaneously polish the end faces facing each other of the substrate held on the rotated center table, respectively.
 21. A polishing apparatus comprising: a table unit, having a substrate mounted thereon, for fixedly holding the substrate in a reference state; four polishing units each including a polishing grind stone for polishing one of four respective end faces of the substrate held on the table unit and substrate side edge portion supporting means for supporting respective lower face of a side edge portion of the substrate in a vicinity of the respective end face of the substrate to be polished by the respective grind stone; four unit moving means each for moving, together with the respective substrate side edge portion supporting means, the respective polishing unit along the respective end face of the substrate while each polishing grind stone is polishing the respective end face of the substrate; and four polishing unit transfer mechanism each for moving the respective polishing unit in a direction to move closer to or away from the respective end face of the substrate.
 22. A polishing apparatus according to claim 21, wherein an image capturing device is provided on each polishing unit, the image capturing device being for capturing an image of an alignment mark provided on the substrate and capturing a polishing site by each polishing grind stone, the polishing apparatus further comprising: an image processing device for computing image data of the alignment mark and the polishing site obtained from each image capturing device; and a control section for computing a rotation angle with respect to the reference state of the substrate mounted on the center unit based on positional data of the alignment mark computed by the image processing device and for computing a polishing amount of each end face to control the respective polishing unit transfer mechanism.
 23. A polishing apparatus according to claim 22, wherein each polishing unit includes an air blowing device between the image capturing device and the polishing grind stone, respectively, for blowing air on the respective image capturing device.
 24. A polishing method for an end face of a substrate by a polishing apparatus according to claim 1, comprising: a holding step of mounting the substrate on the table unit and fixedly holding the substrate in the reference state by the table unit; a supporting step of supporting a side edge portion of the substrate held on the table unit by the substrate side edge portion supporting means of the first polishing unit; and a moving step of moving, while the polishing grind stone of the first polishing unit is polishing the end face of the side edge portion supported by the substrate side edge portion supporting means, the first polishing unit along the end face being polished by the first polishing unit moving means.
 25. A polishing method according to claim 24, wherein the first polishing unit of the polishing apparatus includes substrate side edge portion holding means for holding an upper surface of the side edge portion of the substrate supported by the substrate side edge portion supporting means, the method further comprising: a holding step of the substrate side edge portion holding means holding, subsequent to the supporting step, the upper surface of the side edge portion of the substrate supported by the substrate side edge portion supporting means.
 26. A polishing method according to claim 24, wherein the center table includes suction means for suctioning a central portion of the substrate, and in the holding step, the central portion of the substrate is suctioned by the suction means of the center table.
 27. A polishing method according to claim 26, wherein the table unit of the polishing apparatus includes a plurality of substrate auxiliary supporting means, the plurality of substrate auxiliary supporting means being arranged around the center table to respectively support side portions of the lower surface of the substrate held on the center table, and in the holding step, a side portion of a lower surface of the substrate fixedly held on the center table is supported by at least one of the plurality of substrate auxiliary supporting means.
 28. A polishing method according to claim 27, wherein the substrate auxiliary supporting means of the polishing apparatus includes a sliding mechanism for sliding the auxiliary supporting base to move closer or away from the center table, and in the holding step, the substrate auxiliary supporting means is slid to support the side portion of the substrate fixedly held on the center table.
 29. A polishing method according to claim 24, wherein the table unit of the polishing apparatus includes a table rotating mechanism for rotating the center table, and in the holding step, the end face of the substrate is rotated by the rotating mechanism so as to be along a moving direction of the first polishing unit by the first polishing unit moving means.
 30. A polishing method according to claim 24, wherein the first polishing unit and the first polishing unit moving means of the polishing apparatus are attached to a first polishing unit holding body, the first polishing unit holding body having a horizontal beam being arranged along the end face of the substrate held on the table unit, and the first polishing unit holding body is capable of being translated in a vertical direction with respect to the horizontal beam, and in the moving step, the first polishing unit is moved by the first polishing unit holding body while the first polishing unit is moved so as to be along the end face of the substrate by the first polishing unit moving means.
 31. A polishing method for an end face of a substrate by a polishing apparatus according to claim 17, comprising: a holding step of mounting the substrate on the table unit and fixedly holding the substrate in the reference state by the table unit; a supporting step of supporting a side portion of the substrate held on the table unit by the substrate side edge portion supporting means of the first polishing unit; and a moving step of moving, while the polishing grind stone of the first polishing unit is polishing the end face of the side edge portion supported by the substrate side edge portion supporting means, the first polishing unit along the end face being polished by the first polishing unit moving means, the method further comprising the steps of: subsequent to the holding step and prior to the moving step, capturing an alignment mark provided on the substrate held on the table unit by the image capturing device; next, processing image data of the alignment mark by the image capturing device and generating positional data of the alignment mark; and next, computing a rotation angle with respect to the reference state of the substrate based on the positional data of the alignment mark processed by the image capturing device, wherein in the moving step, a movement of the first polishing unit holding body is controlled based on the computed rotation angle such that the first polishing unit moves along the end face of the substrate.
 32. A polishing method for an end face of a substrate by a polishing apparatus according to claim 20, comprising: a holding step of mounting the substrate on the table unit and fixedly holding the substrate in the reference state by the table unit; next, a rotating step of rotating the table unit by a predetermined angle with respect to the reference state of the substrate by the table rotating mechanism; a supporting step of supporting side edge portions facing each other of the substrate held on the table unit by the respective substrate side edge portion supporting means of the first polishing unit and the second polishing unit; and a moving step of moving, while the polishing grind stones of the first polishing unit and the second polishing unit are polishing the respective end faces of the side edge portions supported by the respective substrate side edge portion supporting means, the first polishing unit and the second polishing unit along the respective end faces being polished by the first polishing unit moving means and the first polishing unit holding body and the second polishing unit moving means and the second polishing unit holding body.
 33. A polishing method according to claim 32, wherein the predetermined angle is an angle having a range of 30 degrees to 60 degrees with respect to the reference state.
 34. A polishing method for an end face of a substrate by a polishing apparatus according to claim 22, comprising: a holding step of mounting the substrate on the table unit and fixedly holding the substrate in the reference state by the table unit; and a supporting step of supporting side edge portions of the substrate held on the table unit by the respective substrate side edge portion supporting means of the four first polishing unit; a moving step of moving, while the polishing grind stones of the polishing units are polishing the respective end faces of the side edge portions supported by the respective substrate side edge portion supporting means, the polishing units along the respective end faces being polished by the respective polishing unit moving means.
 35. A polishing method according to claim 34, wherein in the moving step, the method computes a polishing amount of each end face based on image data of the respective polishing site obtained from the respective image capturing device and controls the respective polishing unit transfer mechanism. 